Low pass filter for current mirror

[VERI]

Which is the most efficient way to construction a low pass filter for current mirror on chip? I can use a capacitor of several pF but R value is limited to KΩ so I can't have a low cut off frequency . Could I use a most device as a high value resistor? Ideally I would like to have an RC>300μs



Thanks!

 

[danadakk]

Capacitance multiplier, see if you can get your hands on this
paper -

Capacitance Super Multiplier for Sub-Hertz Low-Pass Integrated Filters

This brief addresses the design of tunable integrated low-pass filters for sub-Hertz frequencies. The required very large time constants are obtained by using the transconductance of MOS transistors with extremely low bias current and integrated capacitors whose value is augmented by a novel...

ieeexplore.ieee.org

Another approach -

US20070090872A1 - Capacitance multiplier circuit for PLL filter - Google Patents

A capacitance multiplier circuit for a filter is provided. The capacitance multiplier circuit capable of adjusting its equivalent capacitance and used in the filter, applied to a Phase Locked Loops (PLLs) circuit, includes a first operational amplifier having a positive input end for receiving...

patents.google.com

Regards, Dana.

 

[biff44]

yes, a capacitor on the base of a bipolar transistor will "look" like a much bigger capacitance at the emitter, due to the transistor gain.