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Vintage threads from the first ten years

opamp imp ques.

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3/18/2000 2:07 AM
JOHN	opamp imp ques. I am making a booster with a TL071.My output has a 100 ohm resistor,a .1uf cap,and a 1 meg pot(one leg to ground).Does the pot or cap effect the impedence

3/18/2000 3:37 AM
Don Symes	The output impedance of the circuit will vary with the pot setting, being the opamp's output impedance + the 100 ohms (if it's in series) + the resistance of the pot segment from the 'top' to the wiper. That 1M seems a bit high, don't know what you plan to do with the cap. What about your feedback path? - not that it's relevant.

3/19/2000 4:55 AM
John	DON,DO I not need the cap?I'm using a single ended power supply so I thought it had to be there.If I used a split supply could I omit the cap?

3/19/2000 4:52 PM
Don Symes	Where is the cap in relation to the op-amp and the other components. It's tough to answer from just a parts list.

3/20/2000 5:52 PM
JOHN	Don,It goes like this, output-resistor-cap-vol-jack.

3/20/2000 9:03 PM
Don Symes	If that cap goes to GND, then it and your 100-ohm series resistor make a low-pass filter that will roll off highs.

3/20/2000 9:05 PM
Don Symes	The power supply type has no relation to the need for that cap. It's just there to roll off highs in your output. Try putting in a switch to see which way you like it.

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