Bode Analyzer query

[mcmahongg]

Hi

I'm using the latest Bode Analyzer app on OS 96 to look at the gain versus frequency of a 10X AC audio opamp circuit. I've independently checked that the gain at low frequency is close to 20dB. The input impedance of the amplifier is high, with low output impedance.

The Bode plot looks much as I expected except that the low frequency gain is shown as 23dB versus the expected 20 dB. Looking at the Red Pitaya output using a scope, while the measurements are taking place, confirms that the input to the amplifier is close to the expected 1 Vpp and the output is close to 10Vpp.

Is the 3dB discrepancy in the result given by the Bode Analyzer due to an impedance issue - e.g. an expected amplifier input or output impedance? If so, how can this be corrected?

thanks for any advice

Gerry

[redpitaya]

Hi,

So you are measuring the gain frequency response of your amplifier where
you connect IN1 and OUT1 on the input of the amplifier and
IN2 on the amplifier output.
As is shown here
http://wiki.redpitaya.com/index.php?title=Bode_analyzer
Regarding that you have amp. gain 10 this mean that output voltage will be around
10V. With this you have 10V on the IN2 so you need to use HV jumper settings
since on LV jumper settings the max input voltage is 1Vpp.
Or you can use lower amplitude on excitation signal let say 0.1V and leave the jumpers on LV settings.

Best

[mcmahongg]

That solved it! Thank you so much for your help!!

Gerry