TINA/Spice/THS4631: Instrumentation amplifier

Hi Sattam,

Would it be possible for you to describe in more detail as to what's not working in the Instrumentation amplifier?
Also, it seems that you are planning on using the THS3201 which is NRND or not recommended for new designs. I would recommend you to switch to the THS3491 or the THS4631 if you are planning on building the Instrumentation amplifier.

Best Regards,
Rohit

Hi Sattam,

you have made dozens of drawing mistakes...

ina.TSC

Kai

Thanks both ,

I try to build high frequency differential   probe but the output is not   the differential input *Gain .I uploaded the new circuit using THS4631 but still does not work.

5315.Instrumentation amplifier22.TSC

Thanks

Sattam

Hi Sattam,

your input signal is much too high and you violate the common mode input voltage range of THS4631. Decrease the input voltage and the circuit will work:

ina1.TSC

Kai

Thanks Kai for your help .Now , I modified  my design to measure voltage between 0-30 V and it looks ok but the frequency is problem because I can't measure the bandwidth .Also when I increase the frequency above 10MHz , the output distorted .In fact ,I need at least 50MHz.

Thanks

Sattam

Instrumentation amplifier3.TSC

Hi Sattam,

for a 24Vpp sine of 50MHz the OPAmp must handle a slew rate of 3800V/µs. So, the THS4631 might not be fast enough.

What is your signal amplitude at 50MHz?

Kai

Thanks again kai
My signal is envelope of LTE signal .The envelope will varies between 28V and 4V.

Hi Sattam,

You should be able to use the THS3491 along with the LMH6702 for the differential to single ended conversion (see below). The TINA-TI model is attached if you want to play around with. I have used an attenuator at the front-end which brings the signal levels down such that the THS3491 can handle.

The other option you can use is the THS3217 with even higher attenuation at the front-end.

Best Regards,

Rohit

THS3491+LMH6702_INA.TSC

Thanks so much Rohit.

The attenuation is too high .I will use this circuit to measure drop voltage over shunt resistor (0.1 ohm ).Thus , I used differential input voltage to emulate voltage drop over shunt resistor but the output is not proportional to the differential voltage. I appreciate Any suggestions.

THS3491+LMH6702_modified.TSC

Thanks

Sattam

Hi all

Could please give me your feedback on the following differential probe circuit .

thanks

Sattam

7178.THS3201-2.TSC

Hi all

Waiting for your feedback.

Thanks

Hi Sattam,

the circuit might be ok, but you don't use it as differential probe circuit, actually, because only one input signal can be seen.

Kai

Hi Kai

I used 0.5 ohm shunt resistor to create differential input.

Thanks

Sattam

Hi Sattam,

is that the signal you expect in your application? Is it only one signal?

Kai

Hi Kai
Yes, it will be one signal. I wanna to use this circuit as current sensor between power supply and power amplifier (50 ohm).

Thanks
Sattam