Problems for Amplifier Section Lecture notes: Sec. 6 F. Najmabadi, - PowerPoint PPT Presentation

Problems for Amplifier Section Lecture notes: Sec. 6 F. Najmabadi, ECE65, Winter 2012

Exercise 1: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations).  This is a common collector amplifier (emitter follower) . o Input at the base, output at the emitter.  It has a emitter-degeneration bias with a voltage divider. F. Najmabadi, ECE65, Winter 2012

Exercise 1: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations). Thevenin form of the Real circuit Bias circuit Voltage divider = = 22 k || 18 k 9 . 90 k R B 22 k = × = 9 4 . 95 V V + BB 22 k 18 k F. Najmabadi, ECE65, Winter 2012

Exercise 1: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations). Bias Calculations Thevenin form of the Voltage divider = = 9 . 9 k 4 . 95 V R V B BB Assume BJT is in Active : = > ≥ 0 . 7 V, 0 and 0 . 7 V V I V BE C CE − = + + BE KVL : 4.95 I R V I R B B BE E E = × β + + + 3 3 4.95 9 . 9 10 /( 1 ) 0 . 7 10 I I E E = ≈ 4 . 05 mA I I × E C 3 - 4.05 10 I = = = = β = µ C 156 mA/V g / 20 . 3 A I I × m - 3 B C 26 10 V T − = + 150 V CE KVL : 9 V I R ≈ = = r A 37 . 0 k CE E E o - 3 4 x 10 I − = + × × 3 3 9 4 10 10 V C CE β V = > = = = = 5 V 0.7 V V V r T 1 . 28 k CE D 0 π I g B m F. Najmabadi, ECE65, Winter 2012

Exercise 1: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations). Real circuit Signal circuit F. Najmabadi, ECE65, Winter 2012

Exercise 1: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations). Amplifier Parameters This is a common collector amplifier (emitter follower) ( || || ) v g r R R = = o m o E L A + v 1 ( || || ) v g r R R i m o E L − = × = 3 ( || || ) 156 10 ( 38 . 8 k || 1 k || 100 k) 151 g r R R m o E L 151 = ≈ 1 A + v 1 151 [ ] = + + β || ( 1 )( || || ) R R r r R R π = i B o E L 156 mA/V [ ] g = + ≈ m 9 . 9 k || 1 . 3 k 194 k 9 . 9 k R = i r 38 . 8 k o = r 1 . 28 k π + || r R R r π = = π = Ω B sig || || 6 . 4 R r r β β o o o F. Najmabadi, ECE65, Winter 2012

Exercise 1: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations). Amplifier Parameters (Cut-off frequency) 1 = f 1 π + p 2 ( ) R R C i sig c 1 1 = = 34 . 2 Hz f − π × + × × p 1 3 6 2 ( 9 . 9 10 0 ) 0 . 47 10 1 = f π + 2 p 2 ( ) R R C 2 o L c 1 = = = 156 mA/V g 3 . 39 Hz f m π + × × × − p 2 3 6 2 (6.4 100 10 ) 0 . 47 10 = = 9 . 9 k R r 38 . 8 k i o = Ω = 13 R r 1 . 28 k π o ≈ + = + = 34 . 2 3 . 4 37 . 6 Hz f f f 1 2 p p p F. Najmabadi, ECE65, Winter 2012

Exercise 2: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations).  This is a common emitter amplifier with R E . Input at the base, output at the collector. o  It has a emitter-degeneration bias with a voltage divider. F. Najmabadi, ECE65, Winter 2012

Exercise 2: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations). Thevenin form of the Real circuit Bias circuit Voltage divider = = 34 k || 5 . 9 k 5 . 0 k R B 5 . 9 k = × = 15 2 . 22 V V + BB 34 k 5 . 9 k F. Najmabadi, ECE65, Winter 2012

Exercise 2: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations). Bias calculations Thevenin form of the Voltage divider = = 5 . 0 k 2 . 22 V R V B BB Assume BJT is in Active : = > ≥ 0 . 7 V, 0 and 0 . 7 V V I V BE C CE − = + + BE KVL : 2.22 I R V I R B B BE E E = × β + + + 3 2.22 5 . 0 10 /( 1 ) 0 . 7 510 I I E E = ≈ 2 . 84 mA I I E C × = β = µ - 3 2.84 10 I / 14 . 2 A I I = = = C 10.9 mA/V B C g × m 3 - 26 10 V T − = + + CE KVL : 15 I R V I R 150 C C CE E E V ≈ = = r A 52 . 8 k − = + × × + 3 3 15 2 . 84 10 ( 10 510 ) V o × 3 - 2 . 84 10 I CE C = > = 10 . 5 V 0.7 V V V β V 0 CE D = = = T r 1 . 83 k π I g B m F. Najmabadi, ECE65, Winter 2012

Exercise 2: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations). Real circuit Signal circuit F. Najmabadi, ECE65, Winter 2012

Exercise 2: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations). Amplifier Parameters This is a CE amplifier with R E ( || ) v g R R ≈ − o m C L + + 1 ( || ) / v g R R R r i m E C L o = = || 1 k || 100 k 0.990k R R C L × − × 3 10 . 9 10 990 v = − = − o 1 . 64 + × − × + 3 1 10 . 9 10 510 0 . 990 / 52 . 8 v = i 10.9 mA/V g m [ ] ≈ + + β = = r 52 . 8 k r 1 . 83 k || ( 1 ) R R r R π π o i B E [ ] = + × = 5 . 0 k || 1 . 83 k 201 0 . 51 k 4 . 8 k R i v R v = = × o i o A     β + v R v R R v   ≈ +   E sig i sig i || 1 R R r   + + o C o   || r R R R     4 , 800 π E B sig = × − = − ( 1 . 64 ) 1 . 59 A + v ≈ = 4 , 800 100 1 . 0 k R R o C F. Najmabadi, ECE65, Winter 2012

Exercise 2: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations). Amplifier Cut-off frequency (2 caps: 2 poles) 1 = f π + p 1 2 ( ) R R C i sig c 1 1 = = 6 . 91 Hz f − π × + × × p 1 3 6 2 ( 4 . 8 10 100 ) 4 . 7 10 1 = = 10.9 mA/V g f π + m 2 p 2 ( ) R R C = = 2 o L c r 52 . 8 k r 1 . 83 k π o 1 = = = = 15 . 8 Hz f 4 . 8 k 1 . 0 k R R π + × × × − 2 p 3 3 9 i o 2 ( 10 100 10 ) 100 10 ≈ + = + = 6 . 9 15 . 8 22 . 7 Hz f f f p p 1 p 2 F. Najmabadi, ECE65, Winter 2012

Exercise 3: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations).  This is a PNP common emitter amplifier (no R E ). Input at the base, output at the collector ( R E is o shorted out by a cap)  It has a emitter-degeneration bias with two voltage sources. F. Najmabadi, ECE65, Winter 2012

Exercise 3: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations). Assume BJT is in Active : = > ≥ Real circuit Bias circuit 0 . 7 V, 0 and 0 . 7 V V I V EB C EC − = × + 3 BE KVL : 3 2 . 3 10 I V E EB = ≈ 1 . 0 mA I I E C = β = µ / 5 . 0 A I I B C − = × + + × − 3 3 CE KVL : 3 2 . 3 10 2 . 3 10 3 I V I E EC C − = − × × 3 3 6 4 . 6 10 10 V EC = > = 1 . 4 V 0.7 V V V EC D 0 -3 10 I = = = C 38.5 mA/V g × m - 3 26 10 V T 150 V ≈ = = A r 150 k o - 3 10 I C β V = = = T r 5 . 26 k π I g F. Najmabadi, ECE65, Winter 2012 B m

Exercise 3: Find the bias point and the amplifier parameters of the circuit below. (Si BJT with β = 200, V A = 150 V, ignore Early effect in bias calculations). Amplifier Parameters Real circuit Signal circuit This is a CE amplifier with no R E v = − o ( || || ) g r R R m o C L v i v = − × − = − 3 o 38.5 10 ( 150 k || 2 . 3 k || 100 k ) 85 . 3 v i R v v = × = = − i o o 85 . 3 A + v R R v v i sig i i = = = || 5 . 26 k R R r r π π i B = || R R r = o C o 38.5 mA/V g m = = 150 k || 2 . 3 k 2 . 27 k R = = o r 150 k r 5 . 26 k π o ≈ + = + = 67 16 82 Hz * Show f f f F. Najmabadi, ECE65, Winter 2012 p p 1 p 2