Download presentation

Presentation is loading. Please wait.

Published byMicah Danvers Modified over 2 years ago

1
Lecture 12 Transistor Bias Section 5.1-5.2

2
K-30/AK-710 FM Wireless Microphone Audio Amplifier Radio Frequency Oscillator Radio Frequency Amplifier

3
Operating Point Analysis and Design

4
Simple Biasing Assumed VBE and β → IB→IC →VC Comments: IB is sensitive to VBE. IC is very sensitive to β.

5
Iteration Solution IC=βIBIC=βIB (Kick off iteration with VBE=0.7)

6
Example 1 IterationVBEIB (uA)IC (mA) 10.711.31.8 20.683411.3171.8 30.683411.3171.8 Assumed: RB=1 Mohms RC=2 Kohm IS=6.734e-15 Beta=155

7
ADS Simulation IB=11.3 uA IC=1.76 mA Beta=155 ParameterADSIteration VBE674 mV683.4 IB11.3 uA11.317 uA IC1.76 mA1.8 mA

8
Execute Iterations in Matlab

9
β Variation ParameterΒ=100Β=155 VBE672.1 mV 683.4 mV IB11.328 uA 11.317 uA IC1.1 mA1.8 mA gm43.6 mS69.2 mS Variation of gm implies that the gain of the amplifier will vary significantly as a function of beta.

10
Resistive Divider Biasing

11
Back of the Envelope Calcuation Assume the base current is negligible, i.e. negligible compared to the current in R1. IC does not depend on Beta!

12
Negligible Base Current V BE =R 3 /(R 1 +R 3 )V CC V BE =5.75/(5.75+17)2.5V=0.631 V I(R1)/IB=110uA/2.10=52.38

13
Sensitivity to Component Variation Nom.1%5% R2 (KOhm) 5.755.80756.037 VBE (mV)623626639 IB (uA)2.102.353.59 IC (uA)229262424 Gm (mS)8.810.116.3 1% error in R2 leads to 14 % error in IC. 5% error in R2 leads to 85 % in IC.

14
Biasing with Emitter Degeneration If R2↑→VP↑→IE↑→VRE↑→small ∆V BE →Small ∆I C An error in VX due to inaccuracies in R1, R2 and VCC is absorbed by RE, leading to a smaller change in VBE.

15
Design Rules V RE should be > 100 mV.

16
ADS Simulation IB=12.4 uA IC=1.91 mA Beta=154

17
Sensitivity to Component Variation Nom.1%5% R3 (KOhm) 6.86.8687.140 VBE (mV)0.68 IB (uA)12.412.513.1 IC (mA)1.911.932.02 Gm (mS)73.574.277.7 1% error in R2 leads to 1.05 % error in IC. 5% error in R2 leads to 5.7 % error in IC.

18
Misc.

19
What if base current is not ignored!

20
Iterative Method Initial assumption: VBE=0.7 V

Similar presentations

OK

RF Amplifier Analysis and Design Critical Specifications: Input impedance: Z in Load Impedance: Z L Frequency of operation (upper and lower 3 dB.

RF Amplifier Analysis and Design Critical Specifications: Input impedance: Z in Load Impedance: Z L Frequency of operation (upper and lower 3 dB.

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on conservation of plants and animals download Ppt on solar eclipse and lunar eclipse Download ppt on cloud computing technology Ppt on interview skills free download Ppt on power system harmonics analysis Ppt on introduction to object-oriented programming in java Ppt on conference call etiquette you need to know Ppt on internet banking in india Ppt on blue ocean strategy Animal sounds for kids ppt on batteries