Op Amp

[kingofjong]

I set up an amplifier circuit using tlc272cp op amp
I check the current using an multimeter but I don't see any gain

I was wondering if some one could tell me where I am going wrong?

I attached a picture of the circuit

 

[davenn]

Hi there
welcome to EP


from the poor photo, there appears to be some problems with your layout

you have a resistor coming off the lower left pin of the chip to that rail that goes along the bottom of the board
BUT you also have a red wire doing the same and shorting out the resistor

that bottom rail is it the + or - rail ------ I think its supposed to be - ( negative)
meaning the top one is the positive one
You also have a blue? wire going from the pot to the top rail but that top rail isn't connected to anything else

because of the poor pic, I cannot tell what way around the chip is connected

Also provide a schematic of the circuit you were trying to construct

cheers
Dave

 

[kingofjong]

I have attached the schematic

 

[davenn]

OK thanks for that

now you need to start rewiring you board to match the circuit

Dave

 

[LvW]

I set up an amplifier circuit using tlc272cp op amp
I check the current using an multimeter but I don't see any gain
I was wondering if some one could tell me where I am going wrong?
I attached a picture of the circuit

1.) It is not clear which current you are speaking of.
For checking the gain it is much more meaningful to measure input and output voltages.

2.) For linear amplification it is necessary to bias the opamp in its linear range. Normally, this is done using dual supply voltages with negative feedback.
You have negative feedback but single supply only. Thus the input voltage at the non-inv. opamp terminal must have a certain positive value for proper biasing. Are you familiar with biasing schemes for single supply?

 

[davenn]

1.) It is not clear which current you are speaking of.
For checking the gain it is much more meaningful to measure input and output voltages.

2.) For linear amplification it is necessary to bias the opamp in its linear range. Normally, this is done using dual supply voltages with negative feedback.
You have negative feedback but single supply only. Thus the input voltage at the non-inv. opamp terminal must have a certain positive value for proper biasing. Are you familiar with biasing schemes for single supply?

all true
But he has to get the circuit wired properly first before worrying about actually doing measurements

Dave

 

[KrisBlueNZ]

For linear amplification it is necessary to bias the opamp in its linear range. Normally, this is done using dual supply voltages with negative feedback. You have negative feedback but single supply only. Thus the input voltage at the non-inv. opamp terminal must have a certain positive value for proper biasing. Are you familiar with biasing schemes for single supply?

That circuit is just an experiment to demonstrate how a single-supply non-inverting amplifier with a gain of 10 (Edit: ... gain of 11...) and a reference voltage of 0V will behave as the non-inverting input voltage is adjusted from 0V to VCC. There is no need to worry about biasing. It is not supposed to amplify any signal. It is just an experiment, designed to facilitate understanding of that op-amp circuit.

Edit: We need to see a good clear picture of the used section of the breadboard, as well as the overview picture.

 

[LvW]

That circuit is just an experiment to demonstrate how a single-supply non-inverting amplifier with a gain of 10 (Edit: ... gain of 11...)

Sorry - I didn´t know too much about the intentions of the questioner. I was of the opinion, he wants to find a proper bias point for some further experiments.

 

[KrisBlueNZ]

It's one of those "100-in-1 experiments"-type kits for learning electronics by tinkering.

 

[kingofjong]

Okay I think I figured it out, I had the wrong wiring. I see a gain in the output when I move the resistor from the first pin to the third pin.

 

[davenn]

please show us another pic of your layout