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User avatar
By pattern
#205041
Hello -

I want to amplify a 0-3.3V DC signal to 0-10V DC using the TSH82. I'm indifferent to whether the output is inverted or not inverted, as I can always switch the output wires. I read through the tutorial but I am still having issues.

I believe I need to solder a jumper on JP5, provide 12V power to +VCC, attach GND to -VEE, and apply 0-2.12V to -IN1. I should be able to read a 4.7X amplified signal with a voltmeter between OUT1 and GND.

It's unclear if there is an issue with my board or if there is something incorrect with the wiring described above. I consistently read 10V between OUT1 and GND, even when I apply no signal to -IN1. Do you have any suggestions? Thank you!
User avatar
By TS-Mark
#205202
Hi pattern,

I believe you have everything configured properly to amplify the 0-3.3V DC to 0-10V DC but I would need to test one to verify it. Just to clarify, are you reading 10V at all times between OUT1 and GND, regardless of the input? Or are you reading it only with nothing connected? It might be that with that pin floating, the op-amp is seeing that small floating voltage and, depending on the gain settings, could cause the behavior you are seeing.

I hope this helps identify the issue but if you continue to have issues, let me know and I can try and test with one here and see if we can figure out what the issue is.
User avatar
By pattern
#205222
Hi Mark,

Thanks for the reply. I ordered a new TSH82 and just tested it. I still read 10V between OUT1 and GND, regardless of the input to -IN1. The output of OUT1 is always identical to +VCC. I also tried grounding -IN1, but the output of OUT1 is still identical to +VCC.

I appreciate the help!

Additional note:
I believe the gain will be over V_ref rather than GND because the amplifier if connected to V_ref.
User avatar
By TS-Mark
#205331
Interesting. I'm going to need to get one of these to play around with. Just so I can make sure I am replicating your circuit properly, can you take a few photos of your board(s) and circuit and attach them to your response?
User avatar
By pattern
#205559
Hi Mark. Thanks, and my apologies for the delay. I ended up purchasing a DAC to provide me with the voltage I need, so I won't be using the TSH82 for my project. If you still want to test the circuit, I'm happy to send you a photo!
User avatar
By TS-Mark
#205561
Hi again,

Not a problem. I'd love to take a look to try and set it up and see if we can identify the issue here. I'm still learning the "magic" behind OpAmps and since this board is so customizable, it's hard to replicate the circuit without photos of it. It may help me or another user identify a simple fix for this problem.
User avatar
By pattern
#205668
Hi Mark,

Attached are two images. The only solder jumper I added is on JP5.

Cheers,
Merritt
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By n1ist
#205680
Two things to keep in mind with this circuit:
- It is an inverting op-amp with a gain of -4.7 so theoretically, an input of 2.12V would give an output of -9.96V, if the rails were sufficient.
- While you are feeding it 12V between Vcc and Vee, it is creating a "0-volt" reference half-way between them (R1 and R2 form a voltage divider, setting Vref (what the op-amp is considering ground at 6V with respect to Vee), and the math is based on this reference.

Think of it as wired up to handle a bipolar signal (such as an AC-coupled audio signal) with a DC bias to offset everything to the half-way point. It's one of the things you get to deal with when you have a single-supply op-amp.