Lec_8_CEDesigns_09 - ESE319 Introduction to...

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ESE319 Introduction to Microelectronics 1 2009 Kenneth R. Laker, update 05Oct09 KRL Common Emitter BJT Amplifier Design Current Mirror Design
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ESE319 Introduction to Microelectronics 2 2009 Kenneth R. Laker, update 05Oct09 KRL Some Observations Conditions for stabilized voltage source biasing Emitter resistance, R E , is needed. Base voltage source will have finite resistance, R B . needs to be much larger than R B . Small R B - relative to R S - will attenuate input signal. Larger R E permits larger R B , but results in lower gain. Gain = - R C /R E for R E >> r e . Split R E with bypass capacitor increases gain. Requires large bypass capacitor. Limiting case - entire R E bypassed: Gain = - g m R C . Simplified rule-of-thumb biasing is adequate. 1  R E
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ESE319 Introduction to Microelectronics 3 2009 Kenneth R. Laker, update 05Oct09 KRL Conflicting Bias and Gain Issues Biasing If R B is small relative to , V B and R E determine I E and, ap- proximately, I C . Stable bias => increase size of R E . Gain Want gain magnitude R C /R E to be “large.” This implies a reduce size of R E . Gain-bias interaction Want R B to be large relative to R S , while still small relative to . Want V CG = V CC – I C R C to be roughly at mid-point between the V CC and the emitter bias voltage, or “1/3, 1/3, 1/3” rule. R C determines bias and gain. 1  R E 1  R E
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ESE319 Introduction to Microelectronics 4 2009 Kenneth R. Laker, update 05Oct09 KRL Design Example Electrical specifications: v s max = 0.1 V pk R S = 50 V CC = 12 V 0 C T 40 C A V = v o max v s max 10 Minimize cost: 1. Minimize bypass capacitors 2. Use standard 5% resistors Design an amplifier to meet the following specifications: More typical gain spec: 9.5 |A V | 10.5 @ midband Requires simulation to verify. f min 20 Hz
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ESE319 Introduction to Microelectronics 5 2009 Kenneth R. Laker, update 05Oct09 KRL Design Step 1 (Choose R B and R E ) Choose an R B >> 10R S : R B 5000 must be 10R B : ≈ 100 R E 10 5000 100 = 500 Nearest standard size * : 470 R E = 470 1  R E * RCA Lab: http://www.ese.upenn.edu/rca/components/passive/listcomponents.html#resistors v s v o
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ESE319 Introduction to Microelectronics 6 2009 Kenneth R. Laker, update 05Oct09 KRL
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This note was uploaded on 11/18/2010 for the course HU 445 taught by Professor Jung during the Spring '10 term at Milwaukee School of Engineering.

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Lec_8_CEDesigns_09 - ESE319 Introduction to...

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