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Electronics => Beginners => Topic started by: dfox416 on March 12, 2014, 05:41:19 am

Title: Single supply op amps
Post by: dfox416 on March 12, 2014, 05:41:19 am

Hello,
Here is what I want to do: operate an op amp single supply (9V and ground) and allow for maximum positive and negative voltage swing (bias at 4.5V). I would like to know how to do it in inverting and non inverting configurations. I have been messing around trying to make this work but I haven't seen a definitive fool-proof way to do it. Some of the circuits I've seen online don't even work in simulation. Can someone post schematics of the correct way to implement an inverting and non inverting op amp in this configuration, AC coupled and DC coupled? Any help would be much appreciated!

Title: Re: Single supply op amps
Post by: Bored@Work on March 12, 2014, 05:55:29 am

http://www.ti.com/lit/ml/sloa091/sloa091.pdf (http://www.ti.com/lit/ml/sloa091/sloa091.pdf)
http://www.ti.com/lit/an/slod006b/slod006b.pdf (http://www.ti.com/lit/an/slod006b/slod006b.pdf)
http://www.ti.com/lit/ds/symlink/lm124-n.pdf (http://www.ti.com/lit/ds/symlink/lm124-n.pdf)

Title: Re: Single supply op amps
Post by: dfox416 on March 12, 2014, 06:14:04 am

I simulated the circuit given on page A-5 of the first link and I got microvolts on the output from a 200mV sine (picture attached). What am I doing wrong?

Title: Re: Single supply op amps
Post by: awallin on March 12, 2014, 06:21:17 am

Quote from: dfox416 on March 12, 2014, 06:14:04 am

I simulated the circuit given on page A-5 of the first link and I got microvolts on the output from a 200mV sine (picture attached). What am I doing wrong?

input also needs to be biased at 4.5V? i.e. sine swings symmetrically around 4.5V - or AC-couple the input with a capacitor after the signal-generator.

Title: Re: Single supply op amps
Post by: dfox416 on March 12, 2014, 06:31:03 am

Thanks. Works perfectly with the capacitor!