OTA Design for Band Pass Filter Applications

[sci-fi_guy]

Hello,

I am trying to design an Operational Transconductance Amplifier (OTA) to be used in the following band pass filter (C⁴ BPF):



It has the following transfer function:



Both Gm₁ and Gm₂ are subthreshold transconductances.

What is the most suitable OTA design/architecture for this filter and how should I select the transistor W/L's?

I am using Cadence with AMS 0.35um 4 metal process (c35b4) technology.

 

[frankrose]

How will you keep constant the subthreshold tranconductances under larger signals? Even in saturation it is complicated. If you want to keep the devices in subthreshold then you should use very high W/L for input devices, to keep area and input capacitance low use minimal length.

 

[erikl]

I'd use one of the simplest 2-stage-OTA configurations, n- or p-input:


W/L ratios depend on necessary current, and this latter one depends on required bandwidth and actual load capacitance.