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Design of Low Power Instrumentation Amplifier

Design of Low Power Instrumentation Amplifier. Instrumentation Amplifier. Design Goal. I want to design an amplifier with more than 40 dB in Gain Less than 10 uA of current. Top Level Schematic. Bias circuit. 1 st stage amplifier. 2 nd stage. Design Strategy.

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Design of Low Power Instrumentation Amplifier

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  1. Design of Low Power Instrumentation Amplifier

  2. Instrumentation Amplifier

  3. Design Goal • I want to design an amplifier with more than 40 dB in Gain • Less than 10 uA of current

  4. Top Level Schematic Bias circuit 1st stage amplifier 2nd stage

  5. Design Strategy • Get a voltage gain of 10 from the first stage (By choosing R1 and RG carefully) • Get the rest of the gain from the second stage • Reuse amplifier cell

  6. Active Loaded Differential Amplifier 2 uA of current Voltage gain of 24.56

  7. Biasing of M3 2 uA of current

  8. Testing of the ECG Circuit (Biasing Circuit)

  9. Low Voltage Cascode Bias Cicuit To keep M2 in saturation: Vx>Vb-Vth→Vx+Vth2>Vb To keep M1 in saturation: VA>Vx-Vth1 Since VA=Vb-VGS2, Vb>Vx-Vth1+VGS2 Design criteria for M2

  10. Vb Requirement Vb=VOD3+VGS4 to produce a minimum output Voltage of VOD3 and VOD4. By design, VGS4=VGS2, VA=VB Vb=VOD2+VTH2+VOD1.

  11. Vb Generation Problem: M5 suffers from no body effect M2 suffers from body effect VGS5=VGS2 VOD1=VGS6-VTH7 Design M7 (Large W7/L7) so that VGS7 is approx. VTH7 Requirement: Vb=VOD2+VTH2+VOD1 Need to have sufficiently large VGS6, otherwise M6=triode since M7=Sat.

  12. Testing of the ECG Circuit (Biasing Circuit)

  13. Biasing Circuitry

  14. Top Level Schematic 2 uA 2 uA 2 uA 2 uA Bias circuit 1st stage amplifier 2nd stage

  15. Gain of the Amplifier

  16. Trasient Simulation Vin,diff=2 mV Vout,single=336 mV Vout,single/Vin,diff=168

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