Stability of linear regulator with any opamp?

[cupoftea]

Hi,
The attached (LTspice and PNG) is a bog standard linear regulator with vin = 20V, for a garment industry application.
Vout can be set anywhere from 0V to 16V.
Usually i(out) is 64mA max.
(Sometimes the load may source up to 100mA to the product, but this actually isnt an intended situation).

Sometimes the regulator is required to pulse the output on and off at 50% duty and T=10ms. (ie from 0V to the regulation voltage and back etc etc)

Do you believe the opamp, with the same shown compensation 47pF, would show good stability if the opamp
were changed for LM324, or LM358, TL074, TL084C, TL084H, OPA1679, MC33174, or LM2902? (ie, any cheap opamp)
....and when in the pulsed output operation, the rise and fall times would be within 50us of each other?

Noting that there is no load capacitance. (the rails of the opamp are 20V and -3v3)


LT1006

https://www.analog.com/en/products/lt1006.html

TL084C

https://www.st.com/en/amplifiers-and-comparators/tl084c.html

TL084H

TL084H data sheet, product information and support | TI.com

TI’s TL084H is a Quad, 40-V, 5.25-MHz, 4-mV offset voltage, 20-V/µs, In to V+ op amp with -40°C to 125°C operation. Find parameters, ordering and quality information

www.ti.com

LM324

LM324 data sheet, product information and support | TI.com

TI’s LM324 is a Quad 30-V 1.2-MHz operational amplifier. Find parameters, ordering and quality information

www.ti.com

LM358

LM358 data sheet, product information and support | TI.com

TI’s LM358 is a Dual, 30-V, 700-kHz operational amplifier. Find parameters, ordering and quality information

www.ti.com

LM2902

LM2902 data sheet, product information and support | TI.com

TI’s LM2902 is a Quad, 26-V 1.2-MHz 2-mV offset voltage operational amplifier. Find parameters, ordering and quality information

www.ti.com

TL074

TL074 data sheet, product information and support | TI.com

TI’s TL074 is a Quad, 30-V, 3-MHz, high slew rate (13-V/µs), In to V+, JFET-input op amp. Find parameters, ordering and quality information

www.ti.com

OPA1679

OPA1679 data sheet, product information and support | TI.com

TI’s OPA1679 is a Low distortion (-120 dB), low noise (4.5nV/rtHz), quad audio op amp. Find parameters, ordering and quality information

www.ti.com

MC33174

https://www.onsemi.com/products/signal-conditioning-control/amplifiers-comparators/operational-amplifiers-op-amps/mc33174

 

[KlausST]

Hi,

there is a local feedback with 47p and about 46kOhms, which results in a cut off frequency of about 72kHz.
Thus I´d say if the OPAMP is unity gain stable and has enough stability at 72kHz and below then it should be stable.

But in either case
* the power supplies of the OPAMP need to be properly decoupled (1)
* the same is true for the current boost stage
* the PCB layout needs to be low impedance and care for low GND bounce (load current related)
* and for sure all other OPAMP specifications (like COMMON mode input voltage range, output current...) need to be satisfied

(1) Sadly simulations work without the decoupling capacitors. Thus they easily get forgotten at the real circuit. Thus I always recommend to add them in the simulation.

Klaus