OPA991: Constant current source scheme

Anna

Part Number: OPA991
Other Parts Discussed in Thread: TLV9062, TLV9002

Hi Dear,

1-The customer is looking for a solution for a constant current source to be used in a temperature control system, referring to Figure 2-16 of the AN-31 amplifier circuit collection file.

zhcaab7d.pdf

2-The voltage requirement of the equipment is 24V-30V, and the current is generally 160mA-1A. The TLV9062 in the picture cannot meet the voltage requirement. If it is replaced with OPA991, is it possible?

3-Are there any other suitable constant current source solutions recommended?

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 273560 points

It is the MOSFET that needs to support the required voltages and currents. The opamp sees only the voltages at the shunt resistor (Rs) and at the MOSFET's gate. Using a 5 V opamp is fine as long as the MOSFET has a low enough R_DS(on) with a 5 V gate voltage.

Riso/C1/RF ensure that the circuit is stable. If you use a different opamp (e.g., a slower TLV9002) or a different MOSFET with a different gate capacitance, you might need to adjust them.

This is the simplest solution for an adjustable, 1-A constant-current sink.

0 Anna over 1 year ago in reply to Clemens Ladisch

Intellectual 940 points

Hi Clemens,

Do you mean that TLV9062 can be replaced with OPA991, but at the same time, it is necessary to modify the parameters of the peripheral circuit to achieve 24V input and 160mA-1A current output?

0 Clemens Ladisch over 1 year ago in reply to Anna

Guru 273560 points

As far as I can see, the TLV9062 does not need to be replaced. The critical component is the MOSFET; I do not know how much power must be dissipated inside it (which depends on how much voltage is dropped over it).

0 Caro Walter over 1 year ago in reply to Clemens Ladisch

TI__Mastermind 18957 points

Hey Anna,

The customer may use the solution found here: https://www.ti.com/tool/CIRCUIT060046

Input:
- Vi = 0 V to 10 V
- Iimax = 200 µA
Output: Io = 0 A to 1 A
Supply:
- Vcc = 15 V
- Vee = 0 V
- Vload = 36 V

All the best,
Carolina

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OPA991: Constant current source scheme