Covert emitter follower to PNP

I don't understand that. The power supplies are ungrounded, so the entire transistor circuit is floating.

John

You are only referencing ground at your input supply, meaning that you've made your self a great, big, fancy, expensive, nonlinear resistor, probably with DC offset.

Where was ground _supposed_ to be in that circuit?

--

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

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

Thank you for your reply. The output ground is in common with the input ground.

The power supplies may or may not be referenced to ground. It seems to work either way. Yes, the 3V DC offset is a desired result.

As stated in my OP I would like to produce a second matching circuit uisng PNP's where the ouptut swings between neg 3 and neg 8V, as opposed to pos 8V and pos 3V.

I have tried a few things to no avail, and can't find anything similar on the net. Any expert advice on this would be much appreciated.

Here is the link again.

Jerry Norris

Try loading it a little.

John

"Jerry Norris" schreef in bericht news: snipped-for-privacy@news.tpg.com.au...

If you replace all transistors by PNP types en revers all voltage sources it should have to work. If not, there's something wrong, probably with the simulator. Be aware that you cannot connect both inputs to the same source.

petrus bitbyter

snipped-for-privacy@news.tpg.com.au...

it

indeed... tell us what problem youre having

NT

Late at night, by candle light, snipped-for-privacy@lightharbor.com (Jerry Norris) penned this immortal opus:

Whatsit supposed to do? Those DC sources are in floating anti-series, effectively making a single floating 6V DC source. Since they have no reference to the signal the whole circuit seems rather pointless.

ITWHBT.

- YD.

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Remove HAT if replying by mail.

I'm still trying to figure out what is covert here! Well the power supply ground could be considered covert.

It's a Stealth Ground.

John

That circuit only works when you clip the scope probe ground to the top of the 3V source, it stops working when you remove the probe.

Well, it's trying to work, but the output amplitude has dropped to 1 volt and there is not the desired neg 3V offset I should have from the neg 3 and neg 9 rails.

Any suggestions please?

Jerry Norris

Yes, the output stage is floating at +6V. The negative of the two supplies could be tied to input signal ground, but I am trying to avoid that if possible.

IOW I want to replace the input signal ground with +3V at the output, so the swing is between +3 to +9 without a common ground reference.

Is everyone saying this is "pointless" because it can't be done, or because it hasn't been done?

Jerry Norris

Almost anything can be done but not if you're not clear on what you want to do. Look at this

$file/AN-107.pdf

It's easy. Just do it right.

John

If I knew how to do it right, would I be here asking for help?

Jerry

Every design starts with an objective specification. Rather than plop down a circuit, it would be far better to know your goal in detail, including the load, bandwidth, THD, etc.

V1 and V2 have no ground reference.

Trying to understand... a single input signal, outputs 3V to 8V, and at -3V and -8V?

Rails of +9V, +3V, -3V and -9V ??

Can you use OpAmps, or are you stuck with using only transistors? ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

It's pointless because a power supply that's not connected to anything can't supply power!

Archimedes said "Give me a lever long enough and a fulcrum on which to place it, and I shall move the world." You've left out the fulcrum -- how is your lever going to move anything?

--

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

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

Larkin doesn't know how to do it, so he attempts to hide his ignorance behind the facade of being an smart-aleck asshole. ...Jim Thompson

-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

| 1962 | I love to cook with wine. Sometimes I even put it in the food.