Open the (mosfet) gate!

Jun 2, 2017

On Friday, June 2, 2017 at 12:34:41 PM UTC-7, rickman wrote:

mrdarrett@gmail.com wrote on 6/2/2017 3:08 PM:
On Friday, June 2, 2017 at 10:34:19 AM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 12:21:52 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson

What are the source/sink current specs on the Arduino output pin?

...Jim Thompson

It looks like 20 mA per pin. The Arduino Uno that I'm using uses an ATmega328p.
https://www.arduino.cc/en/main/arduinoBoardUno

I don't think that is the relevant spec. That number if a guaranteed spec
for continuous operation. To determine the rise/fall time of the gate
voltage you need to know the *actual* current over the range of voltage as
the gate capacitance charges. They may have a curve showing this, but it
won't be a single number.

--

Rick C

Page 455?
http://www.atmel.com/images/Atmel-8271-8-bit-AVR-Microcontroller-ATmega48A-48PA-88A-88PA-168A-168PA-328-328P_datasheet_Complete.pdf

rickman · Jun 2, 2017

mrdarrett@gmail.com wrote on 6/2/2017 3:38 PM:

On Friday, June 2, 2017 at 12:34:41 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/2/2017 3:08 PM:
On Friday, June 2, 2017 at 10:34:19 AM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 12:21:52 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson

What are the source/sink current specs on the Arduino output pin?

...Jim Thompson

It looks like 20 mA per pin. The Arduino Uno that I'm using uses an ATmega328p.
https://www.arduino.cc/en/main/arduinoBoardUno

I don't think that is the relevant spec. That number if a guaranteed spec
for continuous operation. To determine the rise/fall time of the gate
voltage you need to know the *actual* current over the range of voltage as
the gate capacitance charges. They may have a curve showing this, but it
won't be a single number.

--

Rick C

Page 455?
http://www.atmel.com/images/Atmel-8271-8-bit-AVR-Microcontroller-ATmega48A-48PA-88A-88PA-168A-168PA-328-328P_datasheet_Complete.pdf

I believe the relevant graphs are on pages starting at 503. They only show
currents up to 20 mA, but in nearly all cases that happens with just 1 volt
on the I/O pin. So the current drawn reaching that point will be much more
than 20 mA. If the curves were extrapolated I believe they would show
currents of 100 mA or more to start when the output changes state with a 5
volt Vcc. This number would likely be more like 50 mA when running from 3.3
volt Vcc.

--

Rick C

Jim Thompson · Jun 3, 2017

On Fri, 2 Jun 2017 12:38:58 -0700 (PDT), mrdarrett@gmail.com wrote:

On Friday, June 2, 2017 at 12:34:41 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/2/2017 3:08 PM:
On Friday, June 2, 2017 at 10:34:19 AM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 12:21:52 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson

What are the source/sink current specs on the Arduino output pin?

...Jim Thompson

It looks like 20 mA per pin. The Arduino Uno that I'm using uses an ATmega328p.
https://www.arduino.cc/en/main/arduinoBoardUno

I don't think that is the relevant spec. That number if a guaranteed spec
for continuous operation. To determine the rise/fall time of the gate
voltage you need to know the *actual* current over the range of voltage as
the gate capacitance charges. They may have a curve showing this, but it
won't be a single number.

--

Rick C

Page 455?
http://www.atmel.com/images/Atmel-8271-8-bit-AVR-Microcontroller-ATmega48A-48PA-88A-88PA-168A-168PA-328-328P_datasheet_Complete.pdf

480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Jim Thompson · Jun 5, 2017

On Wed, 24 May 2017 08:52:54 -0700 (PDT), mrdarrett@gmail.com wrote:

I was looking at this datasheet:

http://www.irf.com/product-info/datasheets/data/irlz34n.pdf

Rds,on is 0.035 ohm with Vgs=10V (Id=16A) and it's advertised as such on the first page.

But at Vgs=5V (Id=16A) the Rds,on is 0.046 ohm!

I thought it was a logic level mosfet; I thought the gate would be FULLY OPEN at 5V... I guess I was wrong..?

Michael

480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Jim Thompson · Jun 5, 2017

On Mon, 05 Jun 2017 09:31:54 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 24 May 2017 08:52:54 -0700 (PDT), mrdarrett@gmail.com wrote:

I was looking at this datasheet:

http://www.irf.com/product-info/datasheets/data/irlz34n.pdf

Rds,on is 0.035 ohm with Vgs=10V (Id=16A) and it's advertised as such on the first page.

But at Vgs=5V (Id=16A) the Rds,on is 0.046 ohm!

I thought it was a logic level mosfet; I thought the gate would be FULLY OPEN at 5V... I guess I was wrong..?

Michael

Here's a first pass...

http://www.analog-innovations.com/SED/ArduinoBooster.png

...Jim Thompson

480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Jun 5, 2017

On Monday, June 5, 2017 at 10:23:29 AM UTC-7, Jim Thompson wrote:

On Mon, 05 Jun 2017 09:31:54 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 24 May 2017 08:52:54 -0700 (PDT), mrdarrett@gmail.com wrote:

I was looking at this datasheet:

http://www.irf.com/product-info/datasheets/data/irlz34n.pdf

Rds,on is 0.035 ohm with Vgs=10V (Id=16A) and it's advertised as such on the first page.

But at Vgs=5V (Id=16A) the Rds,on is 0.046 ohm!

I thought it was a logic level mosfet; I thought the gate would be FULLY OPEN at 5V... I guess I was wrong..?

Michael

Here's a first pass...

http://www.analog-innovations.com/SED/ArduinoBooster.png

...Jim Thompson

Change Q2 to 2N2369 to minimize storage delay...

http://www.analog-innovations.com/SED/ArduinoBooster_LessDelay.png

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Wow! Thanks!

Just wondering, what are the diodes for? I also thought having two transistors would slow things down even more.

Much appreciated!

Michael

Jim Thompson · Jun 5, 2017

On Mon, 5 Jun 2017 11:49:23 -0700 (PDT), mrdarrett@gmail.com wrote:

On Monday, June 5, 2017 at 10:23:29 AM UTC-7, Jim Thompson wrote:
On Mon, 05 Jun 2017 09:31:54 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 24 May 2017 08:52:54 -0700 (PDT), mrdarrett@gmail.com wrote:

I was looking at this datasheet:

http://www.irf.com/product-info/datasheets/data/irlz34n.pdf

Rds,on is 0.035 ohm with Vgs=10V (Id=16A) and it's advertised as such on the first page.

But at Vgs=5V (Id=16A) the Rds,on is 0.046 ohm!

I thought it was a logic level mosfet; I thought the gate would be FULLY OPEN at 5V... I guess I was wrong..?

Michael

Here's a first pass...

http://www.analog-innovations.com/SED/ArduinoBooster.png

...Jim Thompson

Change Q2 to 2N2369 to minimize storage delay...

http://www.analog-innovations.com/SED/ArduinoBooster_LessDelay.png

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Wow! Thanks!

Just wondering, what are the diodes for? I also thought having two transistors would slow things down even more.

Much appreciated!

Michael

480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

rickman · Jun 5, 2017

mrdarrett@gmail.com wrote on 6/5/2017 2:49 PM:

On Monday, June 5, 2017 at 10:23:29 AM UTC-7, Jim Thompson wrote:
On Mon, 05 Jun 2017 09:31:54 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 24 May 2017 08:52:54 -0700 (PDT), mrdarrett@gmail.com wrote:

I was looking at this datasheet:

http://www.irf.com/product-info/datasheets/data/irlz34n.pdf

Rds,on is 0.035 ohm with Vgs=10V (Id=16A) and it's advertised as such on the first page.

But at Vgs=5V (Id=16A) the Rds,on is 0.046 ohm!

I thought it was a logic level mosfet; I thought the gate would be FULLY OPEN at 5V... I guess I was wrong..?

Michael

Here's a first pass...

http://www.analog-innovations.com/SED/ArduinoBooster.png

...Jim Thompson

Change Q2 to 2N2369 to minimize storage delay...

http://www.analog-innovations.com/SED/ArduinoBooster_LessDelay.png

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Wow! Thanks!

Just wondering, what are the diodes for? I also thought having two transistors would slow things down even more.

When on, the diodes allow Q2 to drain current from the gate while turning
off Q1. In essence the diodes allow the two transistors to act as a
push-pull stage without the extra transistors needed to level shift the
control signal. Q2 both does the level shifting for Q1 and drains the
charge off of the M1 gate.

--

Rick C

Jim Thompson · Jun 6, 2017

On Mon, 5 Jun 2017 11:49:23 -0700 (PDT), mrdarrett@gmail.com wrote:

On Monday, June 5, 2017 at 10:23:29 AM UTC-7, Jim Thompson wrote:
On Mon, 05 Jun 2017 09:31:54 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 24 May 2017 08:52:54 -0700 (PDT), mrdarrett@gmail.com wrote:

I was looking at this datasheet:

http://www.irf.com/product-info/datasheets/data/irlz34n.pdf

Rds,on is 0.035 ohm with Vgs=10V (Id=16A) and it's advertised as such on the first page.

But at Vgs=5V (Id=16A) the Rds,on is 0.046 ohm!

I thought it was a logic level mosfet; I thought the gate would be FULLY OPEN at 5V... I guess I was wrong..?

Michael

Here's a first pass...

http://www.analog-innovations.com/SED/ArduinoBooster.png

...Jim Thompson

Change Q2 to 2N2369 to minimize storage delay...

http://www.analog-innovations.com/SED/ArduinoBooster_LessDelay.png

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Wow! Thanks!

Just wondering, what are the diodes for? I also thought having two transistors would slow things down even more.

Much appreciated!

Michael

480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Jun 6, 2017

On Tuesday, June 6, 2017 at 9:13:50 AM UTC-7, Jim Thompson wrote:

On Mon, 5 Jun 2017 11:49:23 -0700 (PDT), mrdarrett@gmail.com wrote:

On Monday, June 5, 2017 at 10:23:29 AM UTC-7, Jim Thompson wrote:
On Mon, 05 Jun 2017 09:31:54 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 24 May 2017 08:52:54 -0700 (PDT), mrdarrett@gmail.com wrote:

I was looking at this datasheet:

http://www.irf.com/product-info/datasheets/data/irlz34n.pdf

Rds,on is 0.035 ohm with Vgs=10V (Id=16A) and it's advertised as such on the first page.

But at Vgs=5V (Id=16A) the Rds,on is 0.046 ohm!

I thought it was a logic level mosfet; I thought the gate would be FULLY OPEN at 5V... I guess I was wrong..?

Michael

Here's a first pass...

http://www.analog-innovations.com/SED/ArduinoBooster.png

...Jim Thompson

Change Q2 to 2N2369 to minimize storage delay...

http://www.analog-innovations.com/SED/ArduinoBooster_LessDelay.png

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Wow! Thanks!

Just wondering, what are the diodes for? I also thought having two transistors would slow things down even more.

Much appreciated!

Michael

Currents displayed...

http://www.analog-innovations.com/SED/ArduinoBooster_LessDelay_Currents.png

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Is PSpice better than LTSpice? Those are nifty graphs you have there.

100 kHz, 50% duty cycle? From the graphs, it looks like about 10 microseconds pass for one period.

Michael

Jim Thompson · Jun 6, 2017

On Tue, 6 Jun 2017 10:25:27 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, June 6, 2017 at 9:13:50 AM UTC-7, Jim Thompson wrote:
On Mon, 5 Jun 2017 11:49:23 -0700 (PDT), mrdarrett@gmail.com wrote:

On Monday, June 5, 2017 at 10:23:29 AM UTC-7, Jim Thompson wrote:
On Mon, 05 Jun 2017 09:31:54 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 24 May 2017 08:52:54 -0700 (PDT), mrdarrett@gmail.com wrote:

I was looking at this datasheet:

http://www.irf.com/product-info/datasheets/data/irlz34n.pdf

Rds,on is 0.035 ohm with Vgs=10V (Id=16A) and it's advertised as such on the first page.

But at Vgs=5V (Id=16A) the Rds,on is 0.046 ohm!

I thought it was a logic level mosfet; I thought the gate would be FULLY OPEN at 5V... I guess I was wrong..?

Michael

Here's a first pass...

http://www.analog-innovations.com/SED/ArduinoBooster.png

...Jim Thompson

Change Q2 to 2N2369 to minimize storage delay...

http://www.analog-innovations.com/SED/ArduinoBooster_LessDelay.png

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Wow! Thanks!

Just wondering, what are the diodes for? I also thought having two transistors would slow things down even more.

Much appreciated!

Michael

Currents displayed...

http://www.analog-innovations.com/SED/ArduinoBooster_LessDelay_Currents.png

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Is PSpice better than LTSpice? Those are nifty graphs you have there.

Just a wee bit. But it's not free. When I first purchased it (late
'80's) it cost me $8K, plus about $1500/year "maintenance". I've
since discontinued maintenance since Cadence is intent on killing it
as a tool useful for chip design, and started removing features.
(Fortunately, at that time, PSpice was entirely .INI configured, so it
was easy to fix Cadence's hatchet job.)

100 kHz, 50% duty cycle?

Yep. Chosen arbitrarily for illustration.

From the graphs, it looks like about 10 microseconds pass for one period.

Michael

480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Jun 7, 2017

On Tuesday, June 6, 2017 at 10:32:06 AM UTC-7, Jim Thompson wrote:

On Tue, 6 Jun 2017 10:25:27 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, June 6, 2017 at 9:13:50 AM UTC-7, Jim Thompson wrote:
On Mon, 5 Jun 2017 11:49:23 -0700 (PDT), mrdarrett@gmail.com wrote:

On Monday, June 5, 2017 at 10:23:29 AM UTC-7, Jim Thompson wrote:
On Mon, 05 Jun 2017 09:31:54 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 24 May 2017 08:52:54 -0700 (PDT), mrdarrett@gmail.com wrote:

I was looking at this datasheet:

http://www.irf.com/product-info/datasheets/data/irlz34n.pdf

Rds,on is 0.035 ohm with Vgs=10V (Id=16A) and it's advertised as such on the first page.

But at Vgs=5V (Id=16A) the Rds,on is 0.046 ohm!

I thought it was a logic level mosfet; I thought the gate would be FULLY OPEN at 5V... I guess I was wrong..?

Michael

Here's a first pass...

http://www.analog-innovations.com/SED/ArduinoBooster.png

...Jim Thompson

Change Q2 to 2N2369 to minimize storage delay...

http://www.analog-innovations.com/SED/ArduinoBooster_LessDelay.png

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Wow! Thanks!

Just wondering, what are the diodes for? I also thought having two transistors would slow things down even more.

Much appreciated!

Michael

Currents displayed...

http://www.analog-innovations.com/SED/ArduinoBooster_LessDelay_Currents.png

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

Is PSpice better than LTSpice? Those are nifty graphs you have there.

Just a wee bit. But it's not free. When I first purchased it (late
'80's) it cost me $8K, plus about $1500/year "maintenance". I've
since discontinued maintenance since Cadence is intent on killing it
as a tool useful for chip design, and started removing features.
(Fortunately, at that time, PSpice was entirely .INI configured, so it
was easy to fix Cadence's hatchet job.)

100 kHz, 50% duty cycle?

Yep. Chosen arbitrarily for illustration.

From the graphs, it looks like about 10 microseconds pass for one period.

Michael

...Jim Thompson

This is horrifying.

mrdarrett.5gbfree.com/nasty.jpg

Michael

Nov 2, 2017

mrda...@gmail.com wrote:

The bottom line is driving MOSFETs has been done before and optimized. Why
reinvent the wheel?

To make it fun, and to learn something new

newer MOSGET design

amdx · Nov 4, 2017

On 5/24/2017 6:16 PM, rickman wrote:

mrdarrett@gmail.com wrote on 5/24/2017 6:38 PM:
On Wednesday, May 24, 2017 at 3:37:02 PM UTC-7, mrda...@gmail.com wrote:
On Wednesday, May 24, 2017 at 1:27:57 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote:
On Wednesday, May 24, 2017 at 10:53:53 AM UTC-7, John Larkin wrote:
On Wed, 24 May 2017 08:52:54 -0700 (PDT), mrdarrett@gmail.com wrote:

I was looking at this datasheet:

http://www.irf.com/product-info/datasheets/data/irlz34n.pdf

Rds,on is 0.035 ohm with Vgs=10V (Id=16A) and it's advertised as
such on the first page.

But at Vgs=5V (Id=16A) the Rds,on is 0.046 ohm!

I thought it was a logic level mosfet; I thought the gate would
be FULLY OPEN at 5V... I guess I was wrong..?

More gate voltage makes for lower Rds-on. It's a linear device, not a
gate or a switch, despite the word "logic."

Don't trust IR specs anyhow. They are notorious for fudging. This one
might be safe at 10 amps and Vg=10 and a heat sink.

So the moral of the story is, if you want the gate opened *all the
way* with minimum Rds,on, give the gate Vgs,max then?

Ignoring the poor use of nomenclature, yes, (considering the gate to be
a garden gate) higher Vgs opens the gate wider. There will be a point
of maximum effect or at least diminishing returns, but logic FETs will
turn on at logic level voltages, but turn on more fully at higher
voltages. Just don't get carried away and apply 20 volts to a gate
that
is only rated for 10.

--

Rick C

Ah ok, open means open-circuit.

I'm just imagining the King ordering the guards, "Open the gate!" and
they open it to 90% only, and the King bumps his head on the
partially-open gate as he rides in on his horse.

Michael

King: "I said to open the gate!"
Guards: "We did! The specs said it's open!"
King: "OFF WITH HIS HEAD!"

lol

Here's a hard working FET driver,
http://www.mouser.com/ds/2/268/21420d-72995.pdf

Seems like it would have been summoned for other uses, but I have
not seen any circuits.
Mikek

John Larkin · Nov 5, 2017

On Sat, 4 Nov 2017 09:57:10 -0500, amdx <nojunk@knology.net> wrote:

On 5/24/2017 6:16 PM, rickman wrote:
mrdarrett@gmail.com wrote on 5/24/2017 6:38 PM:
On Wednesday, May 24, 2017 at 3:37:02 PM UTC-7, mrda...@gmail.com wrote:
On Wednesday, May 24, 2017 at 1:27:57 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote:
On Wednesday, May 24, 2017 at 10:53:53 AM UTC-7, John Larkin wrote:
On Wed, 24 May 2017 08:52:54 -0700 (PDT), mrdarrett@gmail.com wrote:

I was looking at this datasheet:

http://www.irf.com/product-info/datasheets/data/irlz34n.pdf

Rds,on is 0.035 ohm with Vgs=10V (Id=16A) and it's advertised as
such on the first page.

But at Vgs=5V (Id=16A) the Rds,on is 0.046 ohm!

I thought it was a logic level mosfet; I thought the gate would
be FULLY OPEN at 5V... I guess I was wrong..?

More gate voltage makes for lower Rds-on. It's a linear device, not a
gate or a switch, despite the word "logic."

Don't trust IR specs anyhow. They are notorious for fudging. This one
might be safe at 10 amps and Vg=10 and a heat sink.

So the moral of the story is, if you want the gate opened *all the
way* with minimum Rds,on, give the gate Vgs,max then?

Ignoring the poor use of nomenclature, yes, (considering the gate to be
a garden gate) higher Vgs opens the gate wider. There will be a point
of maximum effect or at least diminishing returns, but logic FETs will
turn on at logic level voltages, but turn on more fully at higher
voltages. Just don't get carried away and apply 20 volts to a gate
that
is only rated for 10.

--

Rick C

Ah ok, open means open-circuit.

I'm just imagining the King ordering the guards, "Open the gate!" and
they open it to 90% only, and the King bumps his head on the
partially-open gate as he rides in on his horse.

Michael

King: "I said to open the gate!"
Guards: "We did! The specs said it's open!"
King: "OFF WITH HIS HEAD!"

lol

Here's a hard working FET driver,
http://www.mouser.com/ds/2/268/21420d-72995.pdf
Seems like it would have been summoned for other uses, but I have
not seen any circuits.
Mikek

Other people make generic 442x series drivers. They are fierce enough
to use alone in lots of cases.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Nov 7, 2017

mrda...@gmail.com wrote:

On Wednesday, May 24, 2017 at 1:27:57 PM UTC-7, rickman wrote:
mrda...@gmail.com wrote:
On Wednesday, May 24, 2017 at 10:53:53 AM UTC-7, John Larkin wrote:
On Wed, 24 May 2017 08:52:54 -0700 (PDT), mrda...@gmail.com wrote:

I was looking at this datasheet:

http://www.irf.com/product-info/datasheets/data/irlz34n.pdf

Rds,on is 0.035 ohm with Vgs=10V (Id=16A) and it's advertised as such on the first page.

But at Vgs=5V (Id=16A) the Rds,on is 0.046 ohm!

I thought it was a logic level mosfet; I thought the gate would be FULLY OPEN at 5V... I guess I was wrong..?

More gate voltage makes for lower Rds-on. It's a linear device, not a
gate or a switch, despite the word "logic."

Don't trust IR specs anyhow. They are notorious for fudging. This one
might be safe at 10 amps and Vg=10 and a heat sink.

So the moral of the story is, if you want the gate opened *all the way* with minimum Rds,on, give the gate Vgs,max then?

Ignoring the poor use of nomenclature, yes, (considering the gate to be
a garden gate) higher Vgs opens the gate wider. There will be a point
of maximum effect or at least diminishing returns, but logic FETs will
turn on at logic level voltages, but turn on more fully at higher
voltages. Just don't get carried away and apply 20 volts to a gate that
is only rated for 10.
--

Ah ok, open means open-circuit.

And semiconductors only emit/drain when its closed.

Open the (mosfet) gate!

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