Ping Jim Thompson

I don't know if you saw my message about what I've been trying to do with the Howlands in the other thread, but I believe you were going to show me how to mirror a Howland output using an opamp and PNP. I'm just kind of at an impass right now and would like some ideas to play around with. No pressure...:-)

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Reply to
bitrex
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I don't mean to be a pest but I am having trouble wrapping my head around t his circuit, as depicted at :

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It seems pretty much useless. What exactly does the thing do ? Act like a S cmitt trigger or something ? On that page the output is coming out of like

500 ohms or something, what makes it better than simple trasistors ? Slew r ate ? If so why not just use a limiter and an amp ?

Does it have to do with transmission line impedance or something ?

I scanned the text on that page and I see pretty much what it does. And dow n a ways is a integrator, I see what that does. What I don't see if why. Th is can be done so many ways, how did it warrant a name ?

Reply to
jurb6006

I simply used an additional output resistor. My loads were balanced anyway (an audio hybrid) so errors were minimal. If you need a four-quadrant current source, I think you're going to pretty much going to need two opamps, if not duplicate the whole thing.

Reply to
krw

The idea is to maintain a constant current at Zl.

Remove Zl and the circuit acts like a schmitt trigger because the load R is beyound what voltage can be supplied to balance it.

With the x2 gain network at the - input and V-divider at the + input, it should maintain balanced (I) at the ZL as Zl R value changes, which of course will change voltage at that node to maintain the disired (I).

Screwing with the input voltages at the input nodes can also allow you to adjust (I) or play with the feed back loop values. You are limited by what the op-amp can hand out. If you have Ltspice drop it in there and see for yourself.

Jamie

Reply to
M Philbrook

When you're so ignorant of circuit design you can't do loop and nodal analysis by hand everything looks useless >:-} ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

I still don't know what you're trying to accomplish... please describe a gozinta/gozouta relationship you're trying to accomplish. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

That seems reasonable.

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Reply to
bitrex

It is better to light a single candle than to curse the darkness.

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Rick
Reply to
rickman

Baaaah! Humbug >:-}

Learn some electronics/math and cut the crap. If you can't understand it, you have no business commenting. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

Or..... if you can't say anything nice.... I'm just sayin'! Crankpot! ;)

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Rick
Reply to
rickman

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