Current to Voltage Converter - Page 1
Forum section: electronics / beginners

author: Md Mubdiul Hasan
author_rank: Regular Contributor
timestamp: December 14, 2017, 08:03:05 am
content: Hello there,I am interested on a Current to Voltage Converter, that basic says, "A current to voltage converter will produce a voltage proportional to the given current".This configuration can be used equally well for devices that source their current via some positive excitation voltage.But I am disappointing what this circuit works ?Could you kindly explain it ?Take a look1. Diodes are used for some purpose, alternatively.2. In ideal case inverting input is a virtual ground, in real case any photo diode is used. but here how the things working!3. Negative feedback contains RC combination.4. Not sure why R2 and C2 has add here, suppress noise?

author: Rerouter
author_rank: Super Contributor
timestamp: December 14, 2017, 08:25:35 am
content: It is a transimpedance amplifier drawn with some extra protection components and some frequency compensation.This amplifuer is generally used where a resistor would not suffice. Or when you need almost no burden voltage. With such a design the burden is as low as the op amps offset voltage.

author: danadak
author_rank: Super Contributor
timestamp: December 14, 2017, 10:33:19 am
content: Some useful ref material -http://www.ti.com/lit/an/snoa515a/snoa515a.pdfhttp://www.tij.co.jp/jp/lit/an/snoa942a/snoa942a.pdfhttps://www.deyisupport.com/cfs-file.ashx/__key/telligent-evolution-components-attachments/00-52-01-00-00-00-51-82/Transimpedance.pdfRegards, Dana.

author: David Hess
author_rank: Super Contributor
timestamp: December 15, 2017, 04:18:12 am
content: That is the kind of current to voltage converter that would be found in a floating instrumentation application like a bench multimeter. Take special notice of the table which shows which parts are shorted or removed for different input current ranges.Current to voltage converters which use feedback are also known as transimpedance amplifiers so a search for that will turn up lots of practical theory.

author: Md Mubdiul Hasan
author_rank: Regular Contributor
timestamp: December 15, 2017, 04:48:39 am
content: Yes. Well said.But, need to go through detail.

author: Rerouter
author_rank: Super Contributor
timestamp: December 15, 2017, 07:42:27 am
content: ... back to basics it is then,have a go over this for a start,https://en.wikipedia.org/wiki/Transimpedance_amplifierOk, so the feedback resistor is the main thing that governs the rest of the circuit.because the op amp will apply corrective feedback to keep its inputs at the same voltage, as you inject a current in to the - input, the op amp output will begin sinking that current to a negative voltage to keep the "-" input at the same voltage as the "+" which is grounded in that example.As the op amp is sinking that current, the output voltage will be equal to the current times the feedback resistance.now actually know what application you plan to use it for could help clarify whether you need it to work of a single supply, or have a positive output voltage.

author: Md Mubdiul Hasan
author_rank: Regular Contributor
timestamp: December 18, 2017, 05:38:46 am
content: Hello Sir Rerouter,You have nicely present the idea, perhaps some equation might help us to understand,http://electronics-course.com/current-voltage-converter.Yes, The feedback capacitor is usually required to improve stability.My application is working with photodiode current.Can you see the attachment where someone has tried to improve this idea.Explain more kindly.

author: Md Mubdiul Hasan
author_rank: Regular Contributor
timestamp: December 18, 2017, 05:42:39 am
content: QuoteYes, its a crucial point to understanding the application.It might help to set a input sensor type.QuoteCan you find any loading effect in this circuit?

author: David Hess
author_rank: Super Contributor
timestamp: December 18, 2017, 05:52:11 am
content: Quote from: Md Mubdiul Hasan on December 18, 2017, 05:42:39 amThe capacitance of the photodiode is a major problem whether you use a shunt resistance or a transimpedance amplifier. There are lots of application notes about how to use a transimpedance amplifier with a photodiode. Bob Pease discussed it also.http://www.electronicdesign.com/analog/whats-all-transimpedance-amplifier-stuff-anyhow-part-1http://www.ti.com/lit/an/sboa035/sboa035.pdf

author: Md Mubdiul Hasan
author_rank: Regular Contributor
timestamp: December 19, 2017, 01:23:07 am
content: Thank you sir David Hess.Let me go deep insight.I will get back to you soon.