question : cmos push pull amplifier with high slew rate

[cmos_ajay]

Hello, I need a cmos amplifier circuit with high SLEW rate. The load is a RC type with values 200 ohm and 2 nano F.
Max load current is -10mA to +10mA
Supply voltage VDD = 4.5V
Any suggestions or any reference papers for reading ?

 

[erikl]

Here you can download a hopefully appropriate paper: **broken link removed**. It's not exactly meeting your output values, but as you need a slew rate of just 5V/µs, this topology could perhaps be useful for your larger Iload and Cload requirements.

 

[cmos_ajay]

Hello, the amplifier in the attachment is a folded cascode with class AB stage. Is there a suitable 'current limiter' circuit architecture that you can suggest ?? I need to limit the max. current to + /- 10mA

 

[erikl]

I think you'd need an extra LDO with current limitation for the power supply of this type of class AB output stage.
Will cost you around 1V of power supply voltage - and still a relatively large LDO output transistor.

Another possibility would be to introduce resistors in series with the sources of the output stage, controlling short circuit MOSFETs between the gate and source, but this would probably decrease the dynamic output capability of the stage - depending on how much voltage drop is needed to achieve the shut down. Perhaps 100mV (10Ω) or even less, together with a simple diff. input OTA controller could manage this.