LM231: LM231 Clarification sought

Varunesh Kumar

Intellectual 830 points

Part Number: LM231
Other Parts Discussed in Thread: LM331

Hello

We are planning to use this LM231 as V to F & F to V till 100 kHz.

While going thru' your Data Sheet. I came across this recommended Ckt.

While the rest of the Circuit is clear, what is not clear is that NPN Tx and the two resistors

connected to the Current Ref Pin. ( Circled in Red )

Can someone please explain the functionality of this part.

Thanks in advance

Varunesh

over 3 years ago

0 kai klaas69 over 3 years ago

Guru 140200 points

Hi Varunesh,

could be a temperature compensation.

Kai

0 Thomas Kuehl over 3 years ago

TI__Guru* 93105 points

Hi Vanrunesh,

Kai is correct, the 2N2222 base-emitter diode and associated resistors are in place to improve the accuracy of the V-to-F over temperature. We don't have specific information about this particular LM331 temperature compensation scheme. However, there is another similar temperature compensation circuit that Bob Pease presented in his LM331 Application Note C, that details the subject in the Compensating for Temperature Coefficients section:

https://www.ti.com/lit/an/snoa734b/snoa734b.pdf

Bob was the inventor of the LM331.

I hope this helps.

Regards, Thomas

Precision Amplifiers Applications Engineering

0 Varunesh Kumar over 3 years ago in reply to Thomas Kuehl

Intellectual 830 points

Many Thanks to Kai & Thomas.

Greatly appreciate your diligent efforts to dig up such old archives.

Yes, Bob Pease was simply great, was and am a great fan of his.

With warm regards

Varun

Amplifiers

Amplifiers forum

LM231: LM231 Clarification sought