OPA172: Current shifter for VCc=5V instead of VCc= 12v

Tapajit Mondal

Prodigy 165 points

Part Number: OPA172
Other Parts Discussed in Thread: OPA2197, OPA197

Tool/software:

4278.350mA,0mA to 503mA,519mA offset ground shift.TSC

Hi sir ,

last Year we have communicated for Current level shifter circuit .

we have used P1 = XP9561GI

N1 = 2N7002 FOR following circuit which bias by VCc= +12V , but now we required biasing for VCc=+5V .

can it be possible with same P1 and N1 .

Today I have reduced VCC From 12v to 8 V then also load current required are stable but for below 8V load current reduced .

I had attached simulation circuit provided by Mr. Ron mac... Sir

7 months ago

0 Raymond Zhang1 7 months ago

TI__Guru* 77541 points

Hi Tapajit,

OPA172 may not be able to work for the dual stage of current source, where you need to RRIO op amp to work for the topology or at least RRO op amp.

You may have to consider OPA2197, TLV2197 or similar RRIO/RRO op amps for the design topology. And you need to a power Mosfet or BJT to work with the application. 2N7002 is unable to dissipate up to 530mA @8Vdc.

Here is the application note for the circuit. What are the frequency operating range and current rising/falling requirements?

https://www.ti.com/lit/ug/slau502/slau502.pdf?ts=1744924162503&ref_url=https%253A%252F%252Fwww.google.com%252F

For current range voltage to current conversion from 0-503mA is no issues. what do you mean in "519mA offset ground shift"?

I need your design requirements to put together a simulation. Your input is a current source, but it is converter to voltage via 10ohm resistor --> so this circuit is V-to-I converter. Is YIG=8ohm is the load for the application, which a variable current source is driving a Rload.

Best,

Raymond

0 Tapajit Mondal 7 months ago in reply to Raymond Zhang1

Prodigy 165 points

Hi Raymond sir ,

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1334274/opa172-i-need-to-convert-4-input-current-to-4-output-current-is-it-possible/5177071#5177071

This is whole thread that is to be continued for now .

All characteristics of input current and output current drive remain required same now ,just I need to change VCC from +12V to +5V .

0 Raymond Zhang1 7 months ago in reply to Tapajit Mondal

TI__Guru* 77541 points

Hi Mondal,

Both mosfets are p-types. Please provide the NMOS for the left V-I circuit.

is this circuit that you are working on currently? 2N7002 is unable to source 530mA over wide range of temperature. Please specify the left and right branch per the current requirements. It will be easier to tell me what you want rather than to try to figure out what you want from the previous reply.

Best,

Raymond

0 Tapajit Mondal 7 months ago in reply to Raymond Zhang1

Prodigy 165 points

Hi sir ,

Above circuit we have implemented,

With

P1 = XP9561GI

N1 = 2N7002

I want to change VCC = +5V now .

Is it possible with keeping passive components resistor same and to generate 519 to 503mA ?

+1 Raymond Zhang1 7 months ago in reply to Tapajit Mondal

TI__Guru* 77541 points

Hi Mondal,

I am unable to find the P1 (pmosfet) Spice model, so I used IRF9540 to simulate the circuit instead.

OPA197 V-I AC Response 04212025.TSC

I kept everything else as close as you had. OPA172 (not RRO op amp) is unable to support 3.5Vdc input due to its lack of Vcm in the upper range, so you will need to select OPA197 or TLV197 op amp or other low voltage op amps (OPA197 is a lower cost precision op amp). Other low voltage RRIO or RRO op amp will work as well. By adjusting Rp value, you can change the load current Iout by V_delta/Rp.

If you have other questions, please let me know.

Best,

Raymond

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OPA172: Current shifter for VCc=5V instead of VCc= 12v