Simple transistor NOT gate

Allen Bong · Feb 3, 2008

Hi,

Is it possible to construct a simple inverter gate using 1 or 2
transistors and resistors?

I tried the circuit below but it doesn't work at all.

VCC
+
|
|
.-.
| |
| |4K7
'-'
|
+------o OUTPUT
|
1K_ |/
INPUT o-|___|----+---|
| |>
.-. |
| | |
4K7| | |
'-' |
| |
| |
=== ===
GND GND

Allen

(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

Richard Seriani · Feb 3, 2008

"Allen Bong" <allenbsf6502@gmail.com> wrote in message
news:c561da52-94da-4ae7-8d64-8e19ddc3fbf6@v67g2000hse.googlegroups.com...

Hi,

Is it possible to construct a simple inverter gate using 1 or 2
transistors and resistors?

Allen,

Yes, it is possible, and your circuit should work. When you ground the
input, the transistor should be in cut-off and the collector voltage should
be at Vcc. When you apply Vcc to the input, the transistor should saturate
and the collector voltage should be at zero.

Check all connections and check you transistor. If your ciruit still does
not work, in what way is it not working? What type of transistor are you
using? What value of Vcc?

Other options? Google: transistor not gate

Richard

Randy Day · Feb 3, 2008

Allen Bong wrote:

Hi,

Is it possible to construct a simple inverter gate using 1 or 2
transistors and resistors?

I tried the circuit below but it doesn't work at all.

VCC
+
|
|
.-.
| |
| |4K7
'-'
|
+------o OUTPUT
|
1K_ |/
INPUT o-|___|----+---|
| |
.-. |
| | |
4K7| | |
'-' |
| |
| |
=== ===
GND GND

What do you get at the output when input is at
ground? At Vcc?

What kind of transistor? How many volts is Vcc?

You may need to select different resistor values
for a particular transistor type, but it should
work.

The overall circuit is a classic inverting
amplifier, used just about everywhere.

Chris · Feb 3, 2008

On Feb 3, 1:52 am, Allen Bong <allenbsf6...@gmail.com> wrote:

Hi,

Is it possible to construct a simple inverter gate using 1 or 2
transistors and resistors?

I tried the circuit below but it doesn't work at all.

VCC
+
|
|
.-.
| |
| |4K7
'-'
|
+------o OUTPUT
|
1K_ |/
INPUT o-|___|----+---|
| |
.-. |
| | |
4K7| | |
'-' |
| |
| |
=== ==> GND GND

Allen

(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

You've described a perfect transistor inverter, that should work for
logic level inputs. A couple of things to check:

* Make sure you're using an NPN transistor instead of a PNP, a MOSFET,
or something else.

* Recheck your wiring, looking particularly at the pinout of the
transistor. It's easy to assume EBC when it's ECB, or vice versa.

* Use a voltmeter to actually measure the voltage at the input. If
you're driving the input from an open collector transistor or gate
output, no current will be injected into the base of your transistor
when your logic level is "high".

If you run through these three, the transistor has to be defective.
Replace it.

You've got the right answer right in front of you. Make it work.

Cheers
Chris

John Larkin · Feb 3, 2008

On Sun, 3 Feb 2008 08:18:12 -0800 (PST), Chris <cfoley1064@yahoo.com>
wrote:

On Feb 3, 1:52 am, Allen Bong <allenbsf6...@gmail.com> wrote:
Hi,

Is it possible to construct a simple inverter gate using 1 or 2
transistors and resistors?

I tried the circuit below but it doesn't work at all.

VCC
+
|
|
.-.
| |
| |4K7
'-'
|
+------o OUTPUT
|
1K_ |/
INPUT o-|___|----+---|
| |
.-. |
| | |
4K7| | |
'-' |
| |
| |
=== ===
GND GND

Allen

(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

You've described a perfect transistor inverter, that should work for
logic level inputs. A couple of things to check:

* Make sure you're using an NPN transistor instead of a PNP, a MOSFET,
or something else.

* Recheck your wiring, looking particularly at the pinout of the
transistor. It's easy to assume EBC when it's ECB, or vice versa.

* Use a voltmeter to actually measure the voltage at the input. If
you're driving the input from an open collector transistor or gate
output, no current will be injected into the base of your transistor
when your logic level is "high".

If you run through these three, the transistor has to be defective.
Replace it.

You've got the right answer right in front of you. Make it work.

Cheers
Chris

Classic RTL gate: should work.

But if you used this to drive another such gate, the second gate would
serious load down the output voltage of the first one. You could
juggle the resistor values to reduce this effect. Like maybe...

VCC
+
|
|
.-.
| |
| | 1K
'-'
|
+------o OUTPUT
|
10K |/
INPUT o-|___|----+---|
| |
.-. |
| | |
open| | |
'-' |
| |
| |
=== ===
GND GND

John

Tim Wescott · Feb 4, 2008

On Sun, 03 Feb 2008 16:54:44 -0800, Allen Bong wrote:

On Feb 4, 2:29Â am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Sun, 3 Feb 2008 08:18:12 -0800 (PST), Chris <cfoley1...@yahoo.com
wrote:

On Feb 3, 1:52Â am, Allen Bong <allenbsf6...@gmail.com> wrote:
Hi,

Is it possible to construct a simple inverter gate using 1 or 2
transistors and resistors?

I tried the circuit below but it doesn't work at all.

Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â VCC
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â +
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â .-.
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | |4K7
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â '-'
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â +------o OUTPUT
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â 1K_ Â Â Â Â |/
Â Â Â Â INPUT o-|___|----+---|
Â Â Â Â Â Â Â Â Â Â Â Â | Â |
Â Â Â Â Â Â Â Â Â Â Â Â .-. Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â | | Â Â |
Â Â Â Â Â Â Â Â Â Â 4K7| | Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â '-' Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â | Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â | Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â === Â ===
Â Â Â Â Â Â Â Â Â Â Â Â GND Â GND

Allen

(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

You've described a perfect transistor inverter, that should work for
logic level inputs. Â A couple of things to check:

* Make sure you're using an NPN transistor instead of a PNP, a MOSFET,
or something else.

* Recheck your wiring, looking particularly at the pinout of the
transistor. Â It's easy to assume EBC when it's ECB, or vice versa.

* Use a voltmeter to actually measure the voltage at the input. Â If
you're driving the input from an open collector transistor or gate
output, no current will be injected into the base of your transistor
when your logic level is "high".

If you run through these three, the transistor has to be defective.
Replace it.

You've got the right answer right in front of you. Â Make it work.

Cheers
Chris

Classic RTL gate: should work.

But if you used this to drive another such gate, the second gate would
serious load down the output voltage of the first one. You could juggle
the resistor values to reduce this effect. Like maybe...

Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â VCC
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â +
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â .-.
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | | 1K
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â '-'
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â +------o OUTPUT
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â 10K Â Â Â Â |/
Â Â Â Â INPUT o-|___|----+---|
Â Â Â Â Â Â Â Â Â Â Â Â | Â |
Â Â Â Â Â Â Â Â Â Â Â Â .-. Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â | | Â Â |
Â Â Â Â Â Â Â Â Â Â open| | Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â '-' Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â | Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â | Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â === Â ===
Â Â Â Â Â Â Â Â Â Â Â Â GND Â GND

John- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Thanks very much Richard, Randy, Chris & John,

The gate was used to replace a 74LS04 TTL inverter used between the
output of 74LS138 and the LE input of a 74LS373 latch. The clock was
about 1.8Mhz. During a high the transistor conducts fine but during a
low input of short duration, I would not be able to get a high with my
logic probe nor the LE is triggered. The Vcc is 5V and the transistor
is a Japanese 2SC945 general purpose transistor.

I checked with google for a transistor NOT gate and it used 1K at
collector and 10K for the base and input. There was no resistor between
Base and Emitter. And I tried that circuit, it doesn't work too. Where
can I get the schematics for a RTL or DTL not gate?

TIA and regards,

Allen

Plain 'ol transistor circuits can be slooow if you aren't careful. You
should either use a smaller (220 ohm?) resistor on the base, or you
should use a 220 in series with a 1k in parallel with a cap -- something
between 100pF and 1nF should do, but I refuse to go through the math in
my head.

You can get Tiny Logic inverters -- I assume you are purposely avoiding
surface mount parts?

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

Allen Bong · Feb 4, 2008

On Feb 4, 2:29 am, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:

On Sun, 3 Feb 2008 08:18:12 -0800 (PST), Chris <cfoley1...@yahoo.com
wrote:

On Feb 3, 1:52 am, Allen Bong <allenbsf6...@gmail.com> wrote:
Hi,

Is it possible to construct a simple inverter gate using 1 or 2
transistors and resistors?

I tried the circuit below but it doesn't work at all.

VCC
+
|
|
.-.
| |
| |4K7
'-'
|
+------o OUTPUT
|
1K_ |/
INPUT o-|___|----+---|
| |
.-. |
| | |
4K7| | |
'-' |
| |
| |
=== ==> >> GND GND

Allen

(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

You've described a perfect transistor inverter, that should work for
logic level inputs. A couple of things to check:

* Make sure you're using an NPN transistor instead of a PNP, a MOSFET,
or something else.

* Recheck your wiring, looking particularly at the pinout of the
transistor. It's easy to assume EBC when it's ECB, or vice versa.

* Use a voltmeter to actually measure the voltage at the input. If
you're driving the input from an open collector transistor or gate
output, no current will be injected into the base of your transistor
when your logic level is "high".

If you run through these three, the transistor has to be defective.
Replace it.

You've got the right answer right in front of you. Make it work.

Cheers
Chris

Classic RTL gate: should work.

But if you used this to drive another such gate, the second gate would
serious load down the output voltage of the first one. You could
juggle the resistor values to reduce this effect. Like maybe...

VCC
+
|
|
.-.
| |
| | 1K
'-'
|
+------o OUTPUT
|
10K |/
INPUT o-|___|----+---|
| |
.-. |
| | |
open| | |
'-' |
| |
| |
=== ==> >> GND GND

John- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Thanks very much Richard, Randy, Chris & John,

The gate was used to replace a 74LS04 TTL inverter used between the
output of 74LS138 and the LE input of a 74LS373 latch. The clock was
about 1.8Mhz. During a high the transistor conducts fine but during a
low input of short duration, I would not be able to get a high with my
logic probe nor the LE is triggered. The Vcc is 5V and the transistor
is a Japanese 2SC945 general purpose transistor.

I checked with google for a transistor NOT gate and it used 1K at
collector and 10K for the base and input. There was no resistor
between Base and Emitter. And I tried that circuit, it doesn't work
too. Where can I get the schematics for a RTL or DTL not gate?

TIA and regards,

Allen

Allen Bong · Feb 4, 2008

On Feb 4, 8:54 am, Allen Bong <allenbsf6...@gmail.com> wrote:

On Feb 4, 2:29 am, John Larkin

jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Sun, 3 Feb 2008 08:18:12 -0800 (PST), Chris <cfoley1...@yahoo.com
wrote:

On Feb 3, 1:52 am, Allen Bong <allenbsf6...@gmail.com> wrote:
Hi,

Is it possible to construct a simple inverter gate using 1 or 2
transistors and resistors?

I tried the circuit below but it doesn't work at all.

VCC
+
|
|
.-.
| |
| |4K7
'-'
|
+------o OUTPUT
|
1K_ |/
INPUT o-|___|----+---|
| |
.-. |
| | |
4K7| | |
'-' |
| |
| |
=== ==> > >> GND GND

Allen

(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

You've described a perfect transistor inverter, that should work for
logic level inputs. A couple of things to check:

* Make sure you're using an NPN transistor instead of a PNP, a MOSFET,
or something else.

* Recheck your wiring, looking particularly at the pinout of the
transistor. It's easy to assume EBC when it's ECB, or vice versa.

* Use a voltmeter to actually measure the voltage at the input. If
you're driving the input from an open collector transistor or gate
output, no current will be injected into the base of your transistor
when your logic level is "high".

If you run through these three, the transistor has to be defective.
Replace it.

You've got the right answer right in front of you. Make it work.

Cheers
Chris

Classic RTL gate: should work.

But if you used this to drive another such gate, the second gate would
serious load down the output voltage of the first one. You could
juggle the resistor values to reduce this effect. Like maybe...

VCC
+
|
|
.-.
| |
| | 1K
'-'
|
+------o OUTPUT
|
10K |/
INPUT o-|___|----+---|
| |
.-. |
| | |
open| | |
'-' |
| |
| |
=== ==> > >> GND GND

John- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Thanks very much Richard, Randy, Chris & John,

The gate was used to replace a 74LS04 TTL inverter used between the
output of 74LS138 and the LE input of a 74LS373 latch. The clock was
about 1.8Mhz. During a high the transistor conducts fine but during a
low input of short duration, I would not be able to get a high with my
logic probe nor the LE is triggered. The Vcc is 5V and the transistor
is a Japanese 2SC945 general purpose transistor.

I checked with google for a transistor NOT gate and it used 1K at
collector and 10K for the base and input. There was no resistor
between Base and Emitter. And I tried that circuit, it doesn't work
too. Where can I get the schematics for a RTL or DTL not gate?

TIA and regards,

Allen- Hide quoted text -

- Show quoted text -

I have got the datasheet of 2sc945 at

http://www.ortodoxism.ro/datasheets2/8/0u9h25xojqxp8qwzrfi8kxtjsswy.pdf

and the RTL inverter gate at

http://www.play-hookey.com/digital/experiments/rtl_inverter.html

Should I used HFE1 or HFE2 for the current gain of the 2sc945 or
should I get a 2N4124 to make the circuit work?

Allen

Allen Bong · Feb 4, 2008

On Feb 4, 9:19 am, Tim Wescott <t...@seemywebsite.com> wrote:

On Sun, 03 Feb 2008 16:54:44 -0800, Allen Bong wrote:
On Feb 4, 2:29 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Sun, 3 Feb 2008 08:18:12 -0800 (PST), Chris <cfoley1...@yahoo.com
wrote:

On Feb 3, 1:52 am, Allen Bong <allenbsf6...@gmail.com> wrote:
Hi,

Is it possible to construct a simple inverter gate using 1 or 2
transistors and resistors?

I tried the circuit below but it doesn't work at all.

VCC
+
|
|
.-.
| |
| |4K7
'-'
|
+------o OUTPUT
|
1K_ |/
INPUT o-|___|----+---|
| |
.-. |
| | |
4K7| | |
'-' |
| |
| |
=== ==> >> >> GND GND

Allen

(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

You've described a perfect transistor inverter, that should work for
logic level inputs. A couple of things to check:

* Make sure you're using an NPN transistor instead of a PNP, a MOSFET,
or something else.

* Recheck your wiring, looking particularly at the pinout of the
transistor. It's easy to assume EBC when it's ECB, or vice versa.

* Use a voltmeter to actually measure the voltage at the input. If
you're driving the input from an open collector transistor or gate
output, no current will be injected into the base of your transistor
when your logic level is "high".

If you run through these three, the transistor has to be defective.
Replace it.

You've got the right answer right in front of you. Make it work.

Cheers
Chris

Classic RTL gate: should work.

But if you used this to drive another such gate, the second gate would
serious load down the output voltage of the first one. You could juggle
the resistor values to reduce this effect. Like maybe...

VCC
+
|
|
.-.
| |
| | 1K
'-'
|
+------o OUTPUT
|
10K |/
INPUT o-|___|----+---|
| |
.-. |
| | |
open| | |
'-' |
| |
| |
=== ==> >> >> GND GND

John- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Thanks very much Richard, Randy, Chris & John,

The gate was used to replace a 74LS04 TTL inverter used between the
output of 74LS138 and the LE input of a 74LS373 latch. The clock was
about 1.8Mhz. During a high the transistor conducts fine but during a
low input of short duration, I would not be able to get a high with my
logic probe nor the LE is triggered. The Vcc is 5V and the transistor
is a Japanese 2SC945 general purpose transistor.

I checked with google for a transistor NOT gate and it used 1K at
collector and 10K for the base and input. There was no resistor between
Base and Emitter. And I tried that circuit, it doesn't work too. Where
can I get the schematics for a RTL or DTL not gate?

TIA and regards,

Allen

Plain 'ol transistor circuits can be slooow if you aren't careful. You
should either use a smaller (220 ohm?) resistor on the base, or you
should use a 220 in series with a 1k in parallel with a cap -- something
between 100pF and 1nF should do, but I refuse to go through the math in
my head.

You can get Tiny Logic inverters -- I assume you are purposely avoiding
surface mount parts?

--
Tim Wescott
Control systems and communications consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html- Hide quoted text -

- Show quoted text -

Is this the circuit you have in mind?

VCC
|
.-.
| |
| |1K
'-'
|
10k +------o
___ |/
o-|___|-+ -|
| |>
.-. |
| | |
220| | == '-' GND
|
+---+
| |
.-. |
| | ---
1k| | ---1n
'-' |
| |
+---+
|
== GND

(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

Yes, this is just a hobby & fun project and I dont have the gears to
solder a SMD. I am constructing the circuit on a breadboard and if it
works, I would solder it onto a stripboard.

I saw the inverter SMD on the back of the databook. It was made by
Toshiba and part number is TC4S69F. It was a 1989 databook.

Allen

Bob Monsen · Feb 4, 2008

Alan:
Your transtor is saturating when on, and it is probably very slow to come
out of saturation. Try putting a diode from base to collector; that will
keep it from saturating. Here is the circuit:

VCC --------------------------.
|
|
.-.
| | 10k
| |
'-'
|
|
.--->|----o----- out
| |
| |
| |
1k | |
___ | |/
in -------|___|----o-------|
|>
|
|
GND --------------------------'
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

This trick is called a 'baker clamp' for some reason. The diode prevents the
transistor from saturating, thereby increasing the speed at which it can
turn off. This circuit probably won't do more than a few MHz, but you never
know.

Regards,
Bob Monsen

Tim Wescott · Feb 4, 2008

On Sun, 03 Feb 2008 17:46:02 -0800, Allen Bong wrote:

On Feb 4, 9:19Â am, Tim Wescott <t...@seemywebsite.com> wrote:
On Sun, 03 Feb 2008 16:54:44 -0800, Allen Bong wrote:
On Feb 4, 2:29Â am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Sun, 3 Feb 2008 08:18:12 -0800 (PST), Chris
cfoley1...@yahoo.com> wrote:

On Feb 3, 1:52Â am, Allen Bong <allenbsf6...@gmail.com> wrote:
Hi,

Is it possible to construct a simple inverter gate using 1 or 2
transistors and resistors?

I tried the circuit below but it doesn't work at all.

Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â VCC
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â +
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â .-.
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | |4K7
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â '-'
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â +------o OUTPUT
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â 1K_ Â Â Â Â |/
Â Â Â Â INPUT o-|___|----+---|
Â Â Â Â Â Â Â Â Â Â Â Â | Â |
Â Â Â Â Â Â Â Â Â Â Â Â .-. Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â | | Â Â |
Â Â Â Â Â Â Â Â Â Â 4K7| | Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â '-' Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â | Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â | Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â === Â ===
Â Â Â Â Â Â Â Â Â Â Â Â GND Â GND

Allen

(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

You've described a perfect transistor inverter, that should work
for logic level inputs. Â A couple of things to check:

* Make sure you're using an NPN transistor instead of a PNP, a
MOSFET, or something else.

* Recheck your wiring, looking particularly at the pinout of the
transistor. Â It's easy to assume EBC when it's ECB, or vice versa.

* Use a voltmeter to actually measure the voltage at the input. Â If
you're driving the input from an open collector transistor or gate
output, no current will be injected into the base of your
transistor when your logic level is "high".

If you run through these three, the transistor has to be defective.
Replace it.

You've got the right answer right in front of you. Â Make it work.

Cheers
Chris

Classic RTL gate: should work.

But if you used this to drive another such gate, the second gate
would serious load down the output voltage of the first one. You
could juggle the resistor values to reduce this effect. Like
maybe...

Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â VCC
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â +
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â .-.
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â | | 1K
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â '-'
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â +------o OUTPUT
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
Â Â Â Â Â Â Â Â 10K Â Â Â Â |/
Â Â Â Â INPUT o-|___|----+---|
Â Â Â Â Â Â Â Â Â Â Â Â | Â |
Â Â Â Â Â Â Â Â Â Â Â Â .-. Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â | | Â Â |
Â Â Â Â Â Â Â Â Â Â open| | Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â '-' Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â | Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â | Â Â |
Â Â Â Â Â Â Â Â Â Â Â Â === Â ===
Â Â Â Â Â Â Â Â Â Â Â Â GND Â GND

John- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Thanks very much Richard, Randy, Chris & John,

The gate was used to replace a 74LS04 TTL inverter used between the
output of 74LS138 and the LE input of a 74LS373 latch. Â The clock was
about 1.8Mhz. Â During a high the transistor conducts fine but during
a low input of short duration, I would not be able to get a high with
my logic probe nor the LE is triggered. Â The Vcc is 5V and the
transistor is a Japanese 2SC945 general purpose transistor.

I checked with google for a transistor NOT gate and it used 1K at
collector and 10K for the base and input. Â There was no resistor
between Base and Emitter. Â And I tried that circuit, it doesn't work
too. Â Where can I get the schematics for a RTL or DTL not gate?

TIA and regards,

Allen

Plain 'ol transistor circuits can be slooow if you aren't careful. Â You
should either use a smaller (220 ohm?) resistor on the base, or you
should use a 220 in series with a 1k in parallel with a cap --
something between 100pF and 1nF should do, but I refuse to go through
the math in my head.

You can get Tiny Logic inverters -- I assume you are purposely avoiding
surface mount parts?

--
Tim Wescott
Control systems and communications
consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html- Hide
quoted text -

- Show quoted text -

Is this the circuit you have in mind?

VCC
|
.-.
| |
| |1K
'-'
|
10k +------o
___ |/
o-|___|-+ -|
| |
.-. |
| | |
220| | ===
'-' GND
|
+---+
| |
.-. |
| | ---
1k| | ---1n
'-' |
| |
+---+
|
===
GND

(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

Yes, this is just a hobby & fun project and I dont have the gears to
solder a SMD. I am constructing the circuit on a breadboard and if it
works, I would solder it onto a stripboard.

I saw the inverter SMD on the back of the databook. It was made by
Toshiba and part number is TC4S69F. It was a 1989 databook.

Allen

No no! You want the capacitor in the path from the drive to the gate, to
speed up the current into and out of the base:

470pF?
___ .----||-----.
o---|___|--+ ___ +--- to base of xistor
220 '---|___|---'
1k

If you have enough drive this will even forcibly de-saturate a transistor
-- look around on the Zetex web site & you'll find some app notes on this.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

Allen Bong · Feb 4, 2008

On Feb 4, 11:21 am, "Bob Monsen" <rcmon...@gmail.com> wrote:

Alan:
Your transtor is saturating when on, and it is probably very slow to come
out of saturation. Try putting a diode from base to collector; that will
keep it from saturating. Here is the circuit:

VCC --------------------------.
|
|
.-.
| | 10k
| |
'-'
|
|
.--->|----o----- out
| |
| |
| |
1k | |
___ | |/
in -------|___|----o-------|
|
|
|
GND --------------------------'
(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

This trick is called a 'baker clamp' for some reason. The diode prevents the
transistor from saturating, thereby increasing the speed at which it can
turn off. This circuit probably won't do more than a few MHz, but you never
know.

Regards,
Bob Monsen

Hi Bob,

Your circuit works like magic. I am going to read more about this
'baker clamp' diode. Was it mentioned in the AoE?

Thanks again for your help!

Allen

Allen Bong · Feb 4, 2008

On Feb 4, 1:55 pm, Tim Wescott <t...@seemywebsite.com> wrote:

On Sun, 03 Feb 2008 17:46:02 -0800, Allen Bong wrote:
On Feb 4, 9:19 am, Tim Wescott <t...@seemywebsite.com> wrote:
On Sun, 03 Feb 2008 16:54:44 -0800, Allen Bong wrote:
On Feb 4, 2:29 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Sun, 3 Feb 2008 08:18:12 -0800 (PST), Chris
cfoley1...@yahoo.com> wrote:

On Feb 3, 1:52 am, Allen Bong <allenbsf6...@gmail.com> wrote:
Hi,

Is it possible to construct a simple inverter gate using 1 or 2
transistors and resistors?

I tried the circuit below but it doesn't work at all.

VCC
+
|
|
.-.
| |
| |4K7
'-'
|
+------o OUTPUT
|
1K_ |/
INPUT o-|___|----+---|
| |
.-. |
| | |
4K7| | |
'-' |
| |
| |
=== ==> >> >> >> GND GND

Allen

(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

You've described a perfect transistor inverter, that should work
for logic level inputs. A couple of things to check:

* Make sure you're using an NPN transistor instead of a PNP, a
MOSFET, or something else.

* Recheck your wiring, looking particularly at the pinout of the
transistor. It's easy to assume EBC when it's ECB, or vice versa..

* Use a voltmeter to actually measure the voltage at the input. If
you're driving the input from an open collector transistor or gate
output, no current will be injected into the base of your
transistor when your logic level is "high".

If you run through these three, the transistor has to be defective.
Replace it.

You've got the right answer right in front of you. Make it work.

Cheers
Chris

Classic RTL gate: should work.

But if you used this to drive another such gate, the second gate
would serious load down the output voltage of the first one. You
could juggle the resistor values to reduce this effect. Like
maybe...

VCC
+
|
|
.-.
| |
| | 1K
'-'
|
+------o OUTPUT
|
10K |/
INPUT o-|___|----+---|
| |
.-. |
| | |
open| | |
'-' |
| |
| |
=== ==> >> >> >> GND GND

John- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Thanks very much Richard, Randy, Chris & John,

The gate was used to replace a 74LS04 TTL inverter used between the
output of 74LS138 and the LE input of a 74LS373 latch. The clock was
about 1.8Mhz. During a high the transistor conducts fine but during
a low input of short duration, I would not be able to get a high with
my logic probe nor the LE is triggered. The Vcc is 5V and the
transistor is a Japanese 2SC945 general purpose transistor.

I checked with google for a transistor NOT gate and it used 1K at
collector and 10K for the base and input. There was no resistor
between Base and Emitter. And I tried that circuit, it doesn't work
too. Where can I get the schematics for a RTL or DTL not gate?

TIA and regards,

Allen

Plain 'ol transistor circuits can be slooow if you aren't careful. You
should either use a smaller (220 ohm?) resistor on the base, or you
should use a 220 in series with a 1k in parallel with a cap --
something between 100pF and 1nF should do, but I refuse to go through
the math in my head.

You can get Tiny Logic inverters -- I assume you are purposely avoiding
surface mount parts?

--
Tim Wescott
Control systems and communications
consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html-Hide
quoted text -

- Show quoted text -

Is this the circuit you have in mind?

VCC
|
.-.
| |
| |1K
'-'
|
10k +------o
___ |/
o-|___|-+ -|
| |
.-. |
| | |
220| | ==> > '-' GND
|
+---+
| |
.-. |
| | ---
1k| | ---1n
'-' |
| |
+---+
|
==> > GND

(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

Yes, this is just a hobby & fun project and I dont have the gears to
solder a SMD. I am constructing the circuit on a breadboard and if it
works, I would solder it onto a stripboard.

I saw the inverter SMD on the back of the databook. It was made by
Toshiba and part number is TC4S69F. It was a 1989 databook.

Allen

No no! You want the capacitor in the path from the drive to the gate, to
speed up the current into and out of the base:

470pF?
___ .----||-----.
o---|___|--+ ___ +--- to base of xistor
220 '---|___|---'
1k

If you have enough drive this will even forcibly de-saturate a transistor
-- look around on the Zetex web site & you'll find some app notes on this.

--
Tim Wescott
Control systems and communications consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html- Hide quoted text -

- Show quoted text -

HI Tim,

I tried out the circuit but it doesnt work in my application. What do
you meant by "if you have enough drive"? I am driving the circuit
with the output of a 74LS138. Does the 74LS138 have enough drive to
unsaturate the transistor?

I am going to google the Zetex web site to get more info as suggested.

Thanks.

Allen

Tim Wescott · Feb 4, 2008

On Mon, 04 Feb 2008 04:40:07 -0800, Allen Bong wrote:

It sounds like Bob Monsen's solution worked for you. I've done this with
74HC logic, but I'll be damned if I can remember the specific resistor
and capacitor values I used.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

JeffM · Feb 5, 2008

Bob Monsen wrote:

is saturating when on,
and it is probably very slow to come out of saturation.

VCC
|
.-.
| | 10k
| |
'-'
|
.->|---o----- out
1k | |
___ | |/
in --|___|-o----|
|
|
GND

Man, Monson put a lot of empty space in his art

....and Google added a lot of crap to it when it got a hold of it.
http://groups.google.com/group/sci.electronics.basics/msg/30d98ef099b975e9?dmode=source
Could Bob be using an oddball font / character set?
...or is Google "improving" things again?

This trick is called a 'baker clamp' for some reason.
The diode prevents the transistor from saturating,
thereby increasing the speed at which it can turn off.

Allen Bong wrote:
Your circuit works like magic. I am going to read more
about this 'baker clamp' diode. Was it mentioned in the AoE?

Yup.
http://books.google.com/?q=Art-of-Electronics+Baker-clamp+saturation
"Sorry, this page's content is restricted"
I tried anyway so I wouldn't have to walk to the shelf
and the F1_1(|<1/\/6 page crashed Gecko.
http://validator.w3.org/check?uri=http://books.google.com/books?id=bkOMDgwFA28C&pg=PP1&dq=Art-of-Electronics+baker-clamp&ei=65qnR6WkAYHgiQH5zr3QBA&sig=jQFnkt5lCVmTHOpUcItQnM-lVVw
Failed validation, 579 Errors

Opera opened it, but it's true: there's nothing to see there. 8-(

Dead-tree version: It's listed in the index: clamp, Baker; page 908.

Allen Bong · Feb 5, 2008

On Feb 5, 8:40 am, JeffM <jef...@email.com> wrote:

Bob Monsen wrote:
Your [transistor] is saturating when on,
and it is probably very slow to come out of saturation.

VCC
|
.-.
| | 10k
| |
'-'
|
.->|---o----- out
1k | |
___ | |/
in --|___|-o----|
|
|
GND

Man, Monson put a lot of empty space in his art
...and Google added a lot of crap to it when it got a hold of it.http://groups.google.com/group/sci.electronics.basics/msg/30d98ef099b...
Could Bob be using an oddball font / character set?
..or is Google "improving" things again?

This trick is called a 'baker clamp' for some reason.
The diode prevents the transistor from saturating,
thereby increasing the speed at which it can turn off.

Allen Bong wrote:
Your circuit works like magic. I am going to read more
about this 'baker clamp' diode. Was it mentioned in the AoE?

Yup.http://books.google.com/?q=Art-of-Electronics+Baker-clamp+saturation
"Sorry, this page's content is restricted"
I tried anyway so I wouldn't have to walk to the shelf
and the F1_1(|<1/\/6 page crashed Gecko.http://validator.w3.org/check?uri=http://books.google.com/books?id=bk...
Failed validation, 579 Errors

Opera opened it, but it's true: there's nothing to see there. 8-(

Dead-tree version: It's listed in the index: clamp, Baker; page 908.- Hide quoted text -

- Show quoted text -

Hi, you're right! My copy of AoE does have a description on Baker
Clamp on Page 584 and also a full chapter on the 8085 micro too. What
a find! Looks like the book was sitting in my book shelf for toooooo
long and I'm going to reread it from the begining again.

Cheers,

Allen

Rich Grise · Feb 7, 2008

On Mon, 04 Feb 2008 17:54:09 -0800, Allen Bong wrote:

Hi, you're right! My copy of AoE does have a description on Baker
Clamp on Page 584 and also a full chapter on the 8085 micro too. What
a find! Looks like the book was sitting in my book shelf for toooooo
long and I'm going to reread it from the begining again.

If you want even faster switching, try this:
[Bob Monsen drew, but I've modified:]

VCC
|
.-.
| | 10k
added | |
v '-'
~1nF |
.---||---o-->|--o----- out
| | |
| 1K | |
| ___ | |/
in -o-|___|--o----|
|
|
GND

Cheers!
Rich

Allen Bong · Feb 7, 2008

On Feb 7, 8:25 am, Rich Grise <r...@example.net> wrote:

On Mon, 04 Feb 2008 17:54:09 -0800, Allen Bong wrote:
Hi, you're right! My copy of AoE does have a description on Baker
Clamp on Page 584 and also a full chapter on the 8085 micro too. What
a find! Looks like the book was sitting in my book shelf for toooooo
long and I'm going to reread it from the begining again.

If you want even faster switching, try this:
[Bob Monsen drew, but I've modified:]

VCC
|
.-.
| | 10k
added | |
v '-'
~1nF |
.---||---o-->|--o----- out
  | | |
  | 1K    | |
| ___   | |/
in -o-|___|--o----|
|
|
GND

Cheers!
Rich

Thanks Rich,

I do have an 8051 and a PIC16F877 SBC working at 12Mhz and 20Mhz resp.
I will try out the circuit there.

Rgds,

Allen

Allen Bong · Feb 13, 2008

On Feb 4, 1:55 pm, Tim Wescott <t...@seemywebsite.com> wrote:

On Sun, 03 Feb 2008 17:46:02 -0800, Allen Bong wrote:
On Feb 4, 9:19 am, Tim Wescott <t...@seemywebsite.com> wrote:
On Sun, 03 Feb 2008 16:54:44 -0800, Allen Bong wrote:
On Feb 4, 2:29 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Sun, 3 Feb 2008 08:18:12 -0800 (PST), Chris
cfoley1...@yahoo.com> wrote:

On Feb 3, 1:52 am, Allen Bong <allenbsf6...@gmail.com> wrote:
Hi,

Is it possible to construct a simple inverter gate using 1 or 2
transistors and resistors?

I tried the circuit below but it doesn't work at all.

VCC
+
|
|
.-.
| |
| |4K7
'-'
|
+------o OUTPUT
|
1K_ |/
INPUT o-|___|----+---|
| |
.-. |
| | |
4K7| | |
'-' |
| |
| |
=== ==> >> >> >> GND GND

Allen

(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

You've described a perfect transistor inverter, that should work
for logic level inputs. A couple of things to check:

* Make sure you're using an NPN transistor instead of a PNP, a
MOSFET, or something else.

* Recheck your wiring, looking particularly at the pinout of the
transistor. It's easy to assume EBC when it's ECB, or vice versa..

* Use a voltmeter to actually measure the voltage at the input. If
you're driving the input from an open collector transistor or gate
output, no current will be injected into the base of your
transistor when your logic level is "high".

If you run through these three, the transistor has to be defective.
Replace it.

You've got the right answer right in front of you. Make it work.

Cheers
Chris

Classic RTL gate: should work.

But if you used this to drive another such gate, the second gate
would serious load down the output voltage of the first one. You
could juggle the resistor values to reduce this effect. Like
maybe...

VCC
+
|
|
.-.
| |
| | 1K
'-'
|
+------o OUTPUT
|
10K |/
INPUT o-|___|----+---|
| |
.-. |
| | |
open| | |
'-' |
| |
| |
=== ==> >> >> >> GND GND

John- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Thanks very much Richard, Randy, Chris & John,

The gate was used to replace a 74LS04 TTL inverter used between the
output of 74LS138 and the LE input of a 74LS373 latch. The clock was
about 1.8Mhz. During a high the transistor conducts fine but during
a low input of short duration, I would not be able to get a high with
my logic probe nor the LE is triggered. The Vcc is 5V and the
transistor is a Japanese 2SC945 general purpose transistor.

I checked with google for a transistor NOT gate and it used 1K at
collector and 10K for the base and input. There was no resistor
between Base and Emitter. And I tried that circuit, it doesn't work
too. Where can I get the schematics for a RTL or DTL not gate?

TIA and regards,

Allen

Plain 'ol transistor circuits can be slooow if you aren't careful. You
should either use a smaller (220 ohm?) resistor on the base, or you
should use a 220 in series with a 1k in parallel with a cap --
something between 100pF and 1nF should do, but I refuse to go through
the math in my head.

You can get Tiny Logic inverters -- I assume you are purposely avoiding
surface mount parts?

--
Tim Wescott
Control systems and communications
consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html-Hide
quoted text -

- Show quoted text -

Is this the circuit you have in mind?

VCC
|
.-.
| |
| |1K
'-'
|
10k +------o
___ |/
o-|___|-+ -|
| |
.-. |
| | |
220| | ==> > '-' GND
|
+---+
| |
.-. |
| | ---
1k| | ---1n
'-' |
| |
+---+
|
==> > GND

(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

Yes, this is just a hobby & fun project and I dont have the gears to
solder a SMD. I am constructing the circuit on a breadboard and if it
works, I would solder it onto a stripboard.

I saw the inverter SMD on the back of the databook. It was made by
Toshiba and part number is TC4S69F. It was a 1989 databook.

Allen

No no! You want the capacitor in the path from the drive to the gate, to
speed up the current into and out of the base:

470pF?
___ .----||-----.
o---|___|--+ ___ +--- to base of xistor
220 '---|___|---'
1k

If you have enough drive this will even forcibly de-saturate a transistor
-- look around on the Zetex web site & you'll find some app notes on this.

--
Tim Wescott
Control systems and communications consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html- Hide quoted text -

- Show quoted text -

Hi Tim,

I've found the application notes on the zetex web site. It was on P2
& P4 of the pdf file which explains the speeding up of switching, both
the capacitor speedup and baker clamp methods are described.

http://www.zetex.com/3.0/appnotes/apps/an22.pdf

Allen

Simple transistor NOT gate

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