Problem when testing the AD620 amplifier with the function generator

Thread Starter

Linupe

Joined Oct 24, 2022
6
Hello everyone, I have a problem testing the AD620 amplifier using a function generator.
I am injecting a 100mV sinusoid, and with the gain of a 1k resistor, which increases the signal 50 times. In this configuration I would have a 5v signal at the output, but I don't observe anything. What am I doing wrong? GND is common for the battery, function generator and oscilloscope. I'm using two 9v batteries to power the circuit. Follow my circuit.ad620_test.png
 

schmitt trigger

Joined Jul 12, 2010
843
What is the output’s DC level? Is it exactly zero, within a few milivolts from ground?

Why didn’t you build the circuit like the one on figure 48 of the datasheet?
 

Audioguru again

Joined Oct 21, 2019
6,608
The output cannot be "nothing". Instead it MUST have a DC output of about +7.7V, about -7.5V or about 0V.
What is the exact output DC voltage?
EDIT: What input frequency?
 
Last edited:

Thread Starter

Linupe

Joined Oct 24, 2022
6
What is the output’s DC level? Is it exactly zero, within a few milivolts from ground?

Why didn’t you build the circuit like the one on figure 48 of the datasheet?
At the output I have around 35mV.
I tried connecting the circuit in figure 48 of the datasheet, as suggested, but I got no results, just a few millivolts at the output.
 

Thread Starter

Linupe

Joined Oct 24, 2022
6
The output cannot be "nothing". Instead it MUST have a DC output of about +7.7V, about -7.5V or about 0V.
What is the exact output DC voltage?
EDIT: What input frequency?
I get around 30mV at the output.
I'm injecting a 100mV sinusoid, with a frequency of 1kHz.
 

Thread Starter

Linupe

Joined Oct 24, 2022
6
Hi Lin .
How is the signal generator connected?
E
Hi ericgibbs
I'm using a generator with two alligator type test leads, one red and one black. I'm connecting the red one to pin 3, and the black one to pin 2. The black tip of the generator is also connected to 0V. Is it correct?
 

ericgibbs

Joined Jan 29, 2010
18,646
Hi Lin,
That sounds OK.
We recently had a member who had a batch of 3 AD620 all fakes.

Connect a test circuit as though it is a LM741 pinout, check the output.
E
 

Thread Starter

Linupe

Joined Oct 24, 2022
6
Hi Lin,
That sounds OK.
We recently had a member who had a batch of 3 AD620 all fakes.

Connect a test circuit as though it is a LM741 pinout, check the output.
E
With the lm741 I got a signal at the output! My chips are probably having a problem then. Follow the measurement on the oscilloscope. For use as an instrumentation amplifier, which one can I use instead of the ad620? Thank you very much!
 

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