# LM7171 Rectifier for high frequency signal

Discussion in 'Analog & Mixed-Signal Design' started by Z'YonG, Feb 7, 2017.

1. ### Z'YonG Thread Starter Member

Feb 2, 2017
56
1
Hi all,
I wanna design a single power supply rectifier using LM7171 Op Amp, which can process a signal at 5MHz, anyone have any ideas? and also, I have designed one with LM358, it works perfectly at low frequency but not high frequency.
Thank you

2. ### ScottWang Moderator

Aug 23, 2012
6,591
1,021
Do you have a schematic?
How are the input voltage and out voltage (the gain of the amplifier that you want to use)?
How is the signal sine wave or square wave?

LM7171
- unity-gain bandwidth of 200 MHz.

3. ### Z'YonG Thread Starter Member

Feb 2, 2017
56
1
I am not sure if LM7171 is capable for the rectifier, because I only have single power supply. I have used schematic diagram as below to build a rectifier with LM358, it works perfectly fine with low frequency signal. But the signal that I want to process with is 50MHz analog signal, I have already amplified it with LM7171, and now I want to design a peak detector/integrator circuit for it. From what I heard, Before the integrator, I will need a rectifier.
I have tried different design with LM7171, they didn't work...

4. ### ScottWang Moderator

Aug 23, 2012
6,591
1,021
How are the values of R2 and R1?

The LM7171 working in 200Mhz only with Gain=1, it means that gain = R2/R1 = 1.

How is the situation, did you measure it with O'scope?

5. ### Z'YonG Thread Starter Member

Feb 2, 2017
56
1
I know LM7171 working in 200MHz, that is why I use it to design my rectifier. The value of R1 and R2 are 1K ohms. and yes, I tested it on the oscilloscope with circuit diagram I uploaded, it doesn't work at all.

6. ### ScottWang Moderator

Aug 23, 2012
6,591
1,021
Does it means that no any output?

7. ### Z'YonG Thread Starter Member

Feb 2, 2017
56
1
Yes, the output just a straight line, and I have tried different connection, sometime I just get the output that looks the same as input.

8. ### ScottWang Moderator

Aug 23, 2012
6,591
1,021
DO you have Schottky diode to replace 1N4148, do you use 1N41418?
or you just try to do the normal amplifier in 50 Mhz and to see what will be happens?

The other two issues are change the R1, R2 to 100 Ohms and using dual power supply to try

And you didn't mention the Vcc voltage?

9. ### Z'YonG Thread Starter Member

Feb 2, 2017
56
1
I am using 1N4007 here, and we don't have dual power supply. The Vcc voltage is around 3.6V, but it can be changed.