How to build a simple LC oscillator

A

Alexis Bezverkhyy

Guest
Hello !

I'm new to analog electronics (although I've been using uCs for a while)
and I'm trying to build a really simple RC oscillator, a Hartley or a
Colpitts one. All the schematics I've found on the web or in books are
using complex and additionnal components (like 4 pins MOSFETS, JFETS,
transformers...). The two or three models that I've tried to build
weren't oscillating at all. I want to keep it simple to be able to fully
understand what's happening (otherwise I'd have used somme xtal or IC).

Do you know some simple LC oscillator schematics using standard
components that would simply oscillate at few MHz ?

Thanks
 
Alexis Bezverkhyy wrote:
Hello !

I'm new to analog electronics (although I've been using uCs for a while)
and I'm trying to build a really simple RC oscillator, a Hartley or a
Colpitts one. All the schematics I've found on the web or in books are
using complex and additionnal components (like 4 pins MOSFETS, JFETS,
transformers...). The two or three models that I've tried to build
weren't oscillating at all. I want to keep it simple to be able to fully
understand what's happening (otherwise I'd have used somme xtal or IC).

Do you know some simple LC oscillator schematics using standard
components that would simply oscillate at few MHz ?
Click to expand...
A phase shift oscillator using a regular low-cost transistor? Figure 2
shows it:

http://www.uoguelph.ca/~antoon/tutorial/xtor/xtor7/xtor7.html

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
 
On Mon, 15 Dec 2008 23:07:57 +0100, Alexis Bezverkhyy
<bezverky@gmail.com> wrote:

Hello !

I'm new to analog electronics (although I've been using uCs for a while)
and I'm trying to build a really simple RC oscillator, a Hartley or a
Colpitts one. All the schematics I've found on the web or in books are
using complex and additionnal components (like 4 pins MOSFETS, JFETS,
transformers...). The two or three models that I've tried to build
weren't oscillating at all. I want to keep it simple to be able to fully
understand what's happening (otherwise I'd have used somme xtal or IC).

Do you know some simple LC oscillator schematics using standard
components that would simply oscillate at few MHz ?
Click to expand...
---

9V>-------+------+
| |
| [1ľH]
[10K] |
| +------+
| | |
| C |
+----+----B [1000pF]
| | E |
| | |2N3904|
[0.1ľF] | +------+
| | | |
| [3K3] [3K3] [1000pF]
| | | |
GND>-+----+------+------+



Version 4
SHEET 1 880 680
WIRE 256 -80 32 -80
WIRE 448 -80 256 -80
WIRE 256 -32 256 -80
WIRE 448 -32 448 -80
WIRE 448 96 448 48
WIRE 560 96 448 96
WIRE 448 144 448 96
WIRE 560 144 560 96
WIRE 32 192 32 -80
WIRE 256 192 256 48
WIRE 384 192 256 192
WIRE 256 208 256 192
WIRE 256 208 160 208
WIRE 448 256 448 240
WIRE 560 256 560 208
WIRE 560 256 448 256
WIRE 160 272 160 208
WIRE 256 272 256 208
WIRE 448 272 448 256
WIRE 560 288 560 256
WIRE 32 384 32 272
WIRE 160 384 160 336
WIRE 160 384 32 384
WIRE 256 384 256 352
WIRE 256 384 160 384
WIRE 448 384 448 352
WIRE 448 384 256 384
WIRE 560 384 560 352
WIRE 560 384 448 384
WIRE 32 448 32 384
FLAG 32 448 0
SYMBOL ind 432 -48 R0
SYMATTR InstName L1
SYMATTR Value 1e-6
SYMBOL voltage 32 176 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 9
SYMBOL npn 384 144 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL cap 544 144 R0
SYMATTR InstName C2
SYMATTR Value 1000p
SYMBOL cap 544 288 R0
SYMATTR InstName C1
SYMATTR Value 900p
SYMBOL res 432 256 R0
SYMATTR InstName R1
SYMATTR Value 3,3k
SYMBOL res 240 -48 R0
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL res 240 256 R0
SYMATTR InstName R3
SYMATTR Value 3.3k
SYMBOL cap 144 272 R0
SYMATTR InstName C3
SYMATTR Value .1e-6
TEXT 56 408 Left 0 !.tran .002 uic


JF
 
Alexis Bezverkhyy wrote:
Hello !

I'm new to analog electronics (although I've been using uCs for a while)
and I'm trying to build a really simple RC oscillator, a Hartley or a
Colpitts one. All the schematics I've found on the web or in books are
using complex and additionnal components (like 4 pins MOSFETS, JFETS,
transformers...). The two or three models that I've tried to build
weren't oscillating at all. I want to keep it simple to be able to fully
understand what's happening (otherwise I'd have used somme xtal or IC).

Do you know some simple LC oscillator schematics using standard
components that would simply oscillate at few MHz ?

Thanks
If you want a simple OSC and make your own coil, look at a
Click to expand...
Armstrong Oscillator.

That has what is called a tickler coil, another coil is wound
on the same form as the feed back etc..
We use a armstrong variant osc that generates 100Khz at 250 K watts.
It's all one tube!, Very simple.

http://webpages.charter.net/jamie_5"
 
On Mon, 15 Dec 2008 18:06:04 -0600, John Fields wrote:

On Mon, 15 Dec 2008 23:07:57 +0100, Alexis Bezverkhyy
bezverky@gmail.com> wrote:

Hello !

I'm new to analog electronics (although I've been using uCs for a while)
and I'm trying to build a really simple RC oscillator, a Hartley or a
Colpitts one. All the schematics I've found on the web or in books are
using complex and additionnal components (like 4 pins MOSFETS, JFETS,
transformers...). The two or three models that I've tried to build
weren't oscillating at all. I want to keep it simple to be able to fully
understand what's happening (otherwise I'd have used somme xtal or IC).

Do you know some simple LC oscillator schematics using standard
components that would simply oscillate at few MHz ?

---

9V>-------+------+
| |
| [1ÂľH]
[10K] |
| +------+
| | |
| C |
+----+----B [1000pF]
| | E |
| | |2N3904|
[0.1ÂľF] | +------+
| | | |
| [3K3] [3K3] [1000pF]
| | | |
GND>-+----+------+------+



Version 4
SHEET 1 880 680
WIRE 256 -80 32 -80
WIRE 448 -80 256 -80
WIRE 256 -32 256 -80
WIRE 448 -32 448 -80
WIRE 448 96 448 48
WIRE 560 96 448 96
WIRE 448 144 448 96
WIRE 560 144 560 96
WIRE 32 192 32 -80
WIRE 256 192 256 48
WIRE 384 192 256 192
WIRE 256 208 256 192
WIRE 256 208 160 208
WIRE 448 256 448 240
WIRE 560 256 560 208
WIRE 560 256 448 256
WIRE 160 272 160 208
WIRE 256 272 256 208
WIRE 448 272 448 256
WIRE 560 288 560 256
WIRE 32 384 32 272
WIRE 160 384 160 336
WIRE 160 384 32 384
WIRE 256 384 256 352
WIRE 256 384 160 384
WIRE 448 384 448 352
WIRE 448 384 256 384
WIRE 560 384 560 352
WIRE 560 384 448 384
WIRE 32 448 32 384
FLAG 32 448 0
SYMBOL ind 432 -48 R0
SYMATTR InstName L1
SYMATTR Value 1e-6
SYMBOL voltage 32 176 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 9
SYMBOL npn 384 144 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL cap 544 144 R0
SYMATTR InstName C2
SYMATTR Value 1000p
SYMBOL cap 544 288 R0
SYMATTR InstName C1
SYMATTR Value 900p
SYMBOL res 432 256 R0
SYMATTR InstName R1
SYMATTR Value 3,3k
SYMBOL res 240 -48 R0
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL res 240 256 R0
SYMATTR InstName R3
SYMATTR Value 3.3k
SYMBOL cap 144 272 R0
SYMATTR InstName C3
SYMATTR Value .1e-6
TEXT 56 408 Left 0 !.tran .002 uic


JF
Click to expand...
A good healthy bypass cap from 9V to ground is probably essential -- John
forgot to mention it because he bypasses _everything_ (I'm sure).

--
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
 
On Mon, 15 Dec 2008 20:08:51 -0600, Tim Wescott <tim@seemywebsite.com>
wrote:

On Mon, 15 Dec 2008 18:06:04 -0600, John Fields wrote:

On Mon, 15 Dec 2008 23:07:57 +0100, Alexis Bezverkhyy
bezverky@gmail.com> wrote:

Hello !

I'm new to analog electronics (although I've been using uCs for a while)
and I'm trying to build a really simple RC oscillator, a Hartley or a
Colpitts one. All the schematics I've found on the web or in books are
using complex and additionnal components (like 4 pins MOSFETS, JFETS,
transformers...). The two or three models that I've tried to build
weren't oscillating at all. I want to keep it simple to be able to fully
understand what's happening (otherwise I'd have used somme xtal or IC).

Do you know some simple LC oscillator schematics using standard
components that would simply oscillate at few MHz ?

---

9V>-------+------+
| |
| [1ľH]
[10K] |
| +------+
| | |
| C |
+----+----B [1000pF]
| | E |
| | |2N3904|
[0.1ľF] | +------+
| | | |
| [3K3] [3K3] [1000pF]
| | | |
GND>-+----+------+------+



Version 4
SHEET 1 880 680
WIRE 256 -80 32 -80
WIRE 448 -80 256 -80
WIRE 256 -32 256 -80
WIRE 448 -32 448 -80
WIRE 448 96 448 48
WIRE 560 96 448 96
WIRE 448 144 448 96
WIRE 560 144 560 96
WIRE 32 192 32 -80
WIRE 256 192 256 48
WIRE 384 192 256 192
WIRE 256 208 256 192
WIRE 256 208 160 208
WIRE 448 256 448 240
WIRE 560 256 560 208
WIRE 560 256 448 256
WIRE 160 272 160 208
WIRE 256 272 256 208
WIRE 448 272 448 256
WIRE 560 288 560 256
WIRE 32 384 32 272
WIRE 160 384 160 336
WIRE 160 384 32 384
WIRE 256 384 256 352
WIRE 256 384 160 384
WIRE 448 384 448 352
WIRE 448 384 256 384
WIRE 560 384 560 352
WIRE 560 384 448 384
WIRE 32 448 32 384
FLAG 32 448 0
SYMBOL ind 432 -48 R0
SYMATTR InstName L1
SYMATTR Value 1e-6
SYMBOL voltage 32 176 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 9
SYMBOL npn 384 144 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL cap 544 144 R0
SYMATTR InstName C2
SYMATTR Value 1000p
SYMBOL cap 544 288 R0
SYMATTR InstName C1
SYMATTR Value 900p
SYMBOL res 432 256 R0
SYMATTR InstName R1
SYMATTR Value 3,3k
SYMBOL res 240 -48 R0
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL res 240 256 R0
SYMATTR InstName R3
SYMATTR Value 3.3k
SYMBOL cap 144 272 R0
SYMATTR InstName C3
SYMATTR Value .1e-6
TEXT 56 408 Left 0 !.tran .002 uic


JF

A good healthy bypass cap from 9V to ground is probably essential -- John
forgot to mention it because he bypasses _everything_ (I'm sure).
Click to expand...
---
I'm sure you didn't mean to say that I let everything go by unheeded, so
thanks for the kind words and yes, I mostly do. :)

Not an excuse, but SPICE makes it so easy with wires that have no
inductance and voltage sources with zero output impedances that it's
easy to forget what's happening in the real world when working up a
circuit.

On the flip side of the coin, SPICE can model the real world if one can
define it.

Probably the best example of that is JT's success.

BTW, I have an unusual circuit which you might find interesting and
which might make us some money.

May I email it to you?

JF
 
On Mon, 15 Dec 2008 21:57:46 -0600, John Fields wrote:

On Mon, 15 Dec 2008 20:08:51 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

On Mon, 15 Dec 2008 18:06:04 -0600, John Fields wrote:

On Mon, 15 Dec 2008 23:07:57 +0100, Alexis Bezverkhyy
bezverky@gmail.com> wrote:

Hello !

I'm new to analog electronics (although I've been using uCs for a
while) and I'm trying to build a really simple RC oscillator, a
Hartley or a Colpitts one. All the schematics I've found on the web or
in books are using complex and additionnal components (like 4 pins
MOSFETS, JFETS, transformers...). The two or three models that I've
tried to build weren't oscillating at all. I want to keep it simple to
be able to fully understand what's happening (otherwise I'd have used
somme xtal or IC).

Do you know some simple LC oscillator schematics using standard
components that would simply oscillate at few MHz ?

---

9V>-------+------+
| |
| [1ÂľH]
[10K] |
| +------+
| | |
| C |
+----+----B [1000pF]
| | E |
| | |2N3904|
[0.1ÂľF] | +------+
| | | |
| [3K3] [3K3] [1000pF]
| | | |
GND>-+----+------+------+



Version 4
SHEET 1 880 680
WIRE 256 -80 32 -80
WIRE 448 -80 256 -80
WIRE 256 -32 256 -80
WIRE 448 -32 448 -80
WIRE 448 96 448 48
WIRE 560 96 448 96
WIRE 448 144 448 96
WIRE 560 144 560 96
WIRE 32 192 32 -80
WIRE 256 192 256 48
WIRE 384 192 256 192
WIRE 256 208 256 192
WIRE 256 208 160 208
WIRE 448 256 448 240
WIRE 560 256 560 208
WIRE 560 256 448 256
WIRE 160 272 160 208
WIRE 256 272 256 208
WIRE 448 272 448 256
WIRE 560 288 560 256
WIRE 32 384 32 272
WIRE 160 384 160 336
WIRE 160 384 32 384
WIRE 256 384 256 352
WIRE 256 384 160 384
WIRE 448 384 448 352
WIRE 448 384 256 384
WIRE 560 384 560 352
WIRE 560 384 448 384
WIRE 32 448 32 384
FLAG 32 448 0
SYMBOL ind 432 -48 R0
SYMATTR InstName L1
SYMATTR Value 1e-6
SYMBOL voltage 32 176 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 9
SYMBOL npn 384 144 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL cap 544 144 R0
SYMATTR InstName C2
SYMATTR Value 1000p
SYMBOL cap 544 288 R0
SYMATTR InstName C1
SYMATTR Value 900p
SYMBOL res 432 256 R0
SYMATTR InstName R1
SYMATTR Value 3,3k
SYMBOL res 240 -48 R0
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL res 240 256 R0
SYMATTR InstName R3
SYMATTR Value 3.3k
SYMBOL cap 144 272 R0
SYMATTR InstName C3
SYMATTR Value .1e-6
TEXT 56 408 Left 0 !.tran .002 uic


JF

A good healthy bypass cap from 9V to ground is probably essential --
John forgot to mention it because he bypasses _everything_ (I'm sure).

---
I'm sure you didn't mean to say that I let everything go by unheeded, so
thanks for the kind words and yes, I mostly do. :)

Not an excuse, but SPICE makes it so easy with wires that have no
inductance and voltage sources with zero output impedances that it's
easy to forget what's happening in the real world when working up a
circuit.

On the flip side of the coin, SPICE can model the real world if one can
define it.

Probably the best example of that is JT's success.

BTW, I have an unusual circuit which you might find interesting and
which might make us some money.

May I email it to you?

JF
Click to expand...
I'm completely swamped with work that makes me money (thank goodness!),
but send away if you can get the PCB to fit into an email (gawd I'm being
a smartass tonight).

--
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
 
Joerg a écrit :
Alexis Bezverkhyy wrote:
Hello !

I'm new to analog electronics (although I've been using uCs for a while)
and I'm trying to build a really simple RC oscillator, a Hartley or a
Colpitts one. All the schematics I've found on the web or in books are
using complex and additionnal components (like 4 pins MOSFETS, JFETS,
transformers...). The two or three models that I've tried to build
weren't oscillating at all. I want to keep it simple to be able to fully
understand what's happening (otherwise I'd have used somme xtal or IC).

Do you know some simple LC oscillator schematics using standard
components that would simply oscillate at few MHz ?


A phase shift oscillator using a regular low-cost transistor? Figure 2
shows it:

http://www.uoguelph.ca/~antoon/tutorial/xtor/xtor7/xtor7.html
Click to expand...
Thank you a lot, this is what I was looking for !
I'll try to build them tonight.
 
On Mon, 15 Dec 2008 23:07:57 +0100, Alexis
Bezverkhyy <bezverky@gmail.com> wrote:

Hello !

I'm new to analog electronics (although I've been using uCs for a while)
and I'm trying to build a really simple RC oscillator, a Hartley or a
Colpitts one. All the schematics I've found on the web or in books are
using complex and additionnal components (like 4 pins MOSFETS, JFETS,
transformers...). The two or three models that I've tried to build
weren't oscillating at all. I want to keep it simple to be able to fully
understand what's happening (otherwise I'd have used somme xtal or IC).

Do you know some simple LC oscillator schematics using standard
components that would simply oscillate at few MHz ?

Thanks
Click to expand...
If you will be using this to drive digital
circuitry, you can build simple RC oscillators
with CMOS gates that have clean rectangular
outputs. Requires 2 inverter stages (or NAND or
NOR with appropriate inputs ties high/low), one C,
and 1 or 2 Rs. See Don Lancaster's "CMOS
Cookbook" page 225. (At least, it's page 225 in
my ancient edition.)

In fact, if you have a Schmitt-trigger gate like a
CD4093 you only need one gate: Tie one input
high, put your C from the other input to ground,
and the R from that input to the output. Simple!

Best regards,


Bob Masta

DAQARTA v4.51
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!
 
Joerg a écrit :
Alexis Bezverkhyy wrote:
Hello !

I'm new to analog electronics (although I've been using uCs for a while)
and I'm trying to build a really simple RC oscillator, a Hartley or a
Colpitts one. All the schematics I've found on the web or in books are
using complex and additionnal components (like 4 pins MOSFETS, JFETS,
transformers...). The two or three models that I've tried to build
weren't oscillating at all. I want to keep it simple to be able to fully
understand what's happening (otherwise I'd have used somme xtal or IC).

Do you know some simple LC oscillator schematics using standard
components that would simply oscillate at few MHz ?


A phase shift oscillator using a regular low-cost transistor? Figure 2
shows it:

http://www.uoguelph.ca/~antoon/tutorial/xtor/xtor7/xtor7.html
Click to expand...
I've just succeeded in building the phase-shift oscillator (fig. 2).
I did it with a 2N2222 which seems to be almost the same as 2N3904, but
the setting of R6 was quite subtle to make the circuit oscillate.
I could finally probe the RC network with a scope and understand how it
works !

I'll try John's circuit tomorrow.

AB
 
Alexis Bezverkhyy wrote:
Joerg a écrit :
Alexis Bezverkhyy wrote:
Hello !

I'm new to analog electronics (although I've been using uCs for a while)
and I'm trying to build a really simple RC oscillator, a Hartley or a
Colpitts one. All the schematics I've found on the web or in books are
using complex and additionnal components (like 4 pins MOSFETS, JFETS,
transformers...). The two or three models that I've tried to build
weren't oscillating at all. I want to keep it simple to be able to fully
understand what's happening (otherwise I'd have used somme xtal or IC).

Do you know some simple LC oscillator schematics using standard
components that would simply oscillate at few MHz ?

A phase shift oscillator using a regular low-cost transistor? Figure 2
shows it:

http://www.uoguelph.ca/~antoon/tutorial/xtor/xtor7/xtor7.html

I've just succeeded in building the phase-shift oscillator (fig. 2).
I did it with a 2N2222 which seems to be almost the same as 2N3904, but
the setting of R6 was quite subtle to make the circuit oscillate.
I could finally probe the RC network with a scope and understand how it
works !

I'll try John's circuit tomorrow.
Click to expand...
The hfe for the 2222 is quite poor at low currents, see if you have some
small signal BC-type in your junk box. Those are more popular in Europe.

Hey, but at least it worked.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
 
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