Download presentation

Presentation is loading. Please wait.

Published byDrew Bassett Modified about 1 year ago

1
MOS Current Mirror Section 9.2 J. Ou

2
A Simple Current Mirror

3
Example 1

4
Example #2

5
Trade-Offs in Current Mirror Design Output resistance (1/gds) CDS W/L Current

6
I OUT =100 uA L(um)W(um)GDS (uS)CDS (fF) 2109.6351.82100.39 800n47.456.517.13 180n17.0292.91.079 120n13.331470.411 For Same IOUT, L↓→W↓→GDS↑(Ro↓) →CDS ↓ Drop in Ro is not desired.

7
Use Cascode to Increase output Resistance Rout is approximately g m3 r o3 r o2 L1=L2, but L3 need not equal to L2. Design Criteria: Choose V b so that V Y and V X. We will learn how to generate Vb in the next class.

8
Design Example VDS of T4 is not matched to VDS of T5. T4 has VDS of 999.1 mV. How come? Answer: VSD=0.2 was used as design criteria for T0 and T2. We need a transistor to absorb the difference between VDS of T4 (which is 0.6 V) and VSD of T2 (which is 0.2V) Bias I: 100 nA

9
Add More VGS to Minimize Difference in VDS VDS5=161.2 mV gives 50 nA VDS4 is 155.7 mV, provides 49.82nA.

10
Need for a Cascode T1 is designed to have a VSD of 0.4, leading to Vout=0.6 V. T3 is designed to have VDS of 200 mV, but it must sustain Vout=0.6 V. So we need to add a transistor to absorb the difference in V.

11
Property Bias Output Voltage

12
Large Output Resistance

13
Small Signal Gain

Similar presentations

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google