non inverting amplifier

ant17 · May 30, 2013

hi guys i have a lm741 powered by two 9 volt batteries to give me a dual power supply the input connected to a colpits oscillator giving 300mv peak to peak the the feedback resistor from pin 6 to 2 then to negative 100k and 1k but at the output i only get 100mv peak to peak the frequency is 166khz does any body have an idea what i might be doing wrong the oscilloscope is measure between negative and the output pin

crutschow · May 30, 2013

Post your circuit diagram.

godfreyl · May 30, 2013

ant17 said:
feedback resistor from pin 6 to 2 then to negative 100k and 1k

I hope you mean 100K from pin 6 to pin 2, and 1K from pin 2 to the midpoint between the batteries. Also, the input should be DC biased to the midpoint between the batteries as well.

Aside from that the LM741 is very slow, so it's not good for amplification at high frequencies.

ant17 · May 30, 2013

hi guys thanks for your replys i wil try a to send a schematic a little bit later

ant17 · May 30, 2013

hi guys i was unable generate a schematic of my circuit but from whats been said i should have on batteries 0ne postive lead the negative goes to the postive of second battery clip and then i will have a negative and positive supply but i should be taking so called ground connections from the mid point between the two battery clips which is possitive and negative stuck together

godfreyl · May 30, 2013

ant17 said:
i should be taking so called ground connections from the mid point between the two battery clips which is possitive and negative stuck together

Yes, that's right.

LvW · May 30, 2013

ant17 said:
....the frequency is 166khz .....

The 741 type opamp has again of less than 10 at 166 kHz. More than that, the limited slew rate allows not more than some hundreds of mV (output) at that frequency.

ant17 · May 31, 2013

LvW said:
The 741 type op amp has again of less than 10 at 166 kHz. More than that, the limited slew rate allows not more than some hundreds of mV (output) at that frequency.

hi i attacched my circuit the colpits oscillator runs at 166khz yet the output waveform is square wave looking and i am not getting amplification and i don't understand i am roughly putting a 1 to 2 volts peak to peak with out any amplification also i forgot to put a the emitter resistance which is 1k

rahdirs · May 31, 2013

@ant17:in place of 741,try using an opamp with a faster slew rate and better gain at high-frequencies like TL3474

ant17 · May 31, 2013

rahdirs said:
@ant17:in place of 741,try using an opamp with a faster slew rate and better gain at high-frequencies like TL3474

in my circiuit drawing attached to my last post i used a ca3130 opamp but still know sucess

godfreyl · May 31, 2013

You need DC bias for the +input of the opamp. A 100K resistor between the +input and ground should work.

LvW · May 31, 2013

godfreyl said:
You need DC bias for the +input of the opamp. A 100K resistor between the +input and ground should work.

Yes - and, more than that, where is the ground node?

rahdirs · May 31, 2013

LvW said:
Yes - and, more than that, where is the ground node?

The node middle of both batteries must have been the ground node

ant17 · May 31, 2013

rahdirs said:
The node middle of both batteries must have been the ground node

yes the ground node is between the two 9volt batteries

ant17 · Jun 1, 2013

ant17 said:
yes the ground node is between the two 9volt batteries

hi to check if my problems with my op amp are because of frequency so i tryed it at 8khz and found there to be a gain of 3 or 4 and the op amp is a Ca3130 would frequency response be the problem do you think:-(

godfreyl · Jun 1, 2013

Have you fixed the bias? See post 11.

ant17 · Jun 1, 2013

godfreyl said:
Have you fixed the bias? See post 11.

i connected a 100k from the positive pin + but still no amplification even at much lower frequencies using ca3130

godfreyl · Jun 1, 2013

Maybe it's clipping. What are the amplitudes of the input and output signals? Is the DC voltage at the output close to ground with no input, or is it close to + or -9V? Van you show the circuit you're using now?

ant17 · Jun 1, 2013

godfreyl said:
Maybe it's clipping. What are the amplitudes of the input and output signals? Is the DC voltage at the output close to ground with no input, or is it close to + or -9V? Van you show the circuit you're using now?

no its only about 1 to 2volts peak to peak does anybody have a working schematic of a high gain non inverting amplfier that i could try that they know works so i can find out whats wrong

- - - Updated - - -

godfreyl said:
Maybe it's clipping. What are the amplitudes of the input and output signals? Is the DC voltage at the output close to ground with no input, or is it close to + or -9V? Van you show the circuit you're using now?

no its only about 1 to 2volts peak to peak does anybody have a working schematic of a high gain non inverting amplfier that i could try that they know works so i can find out whats wrong

rahdirs · Jun 1, 2013

ant17 said:
does anybody have a working schematic of a high gain non inverting amplfier that i could try that they know works so i can find out whats wrong

Do u need schematic of non-inverting amplifier along with colpitts oscillator???
attached is a high-gain non-inverting amplifier

non inverting amplifier

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