Lect_07 - ECE442 SolidStateDevices&Circuits 7.BJTAmplifiers...

This preview shows pages 1–8. Sign up to view the full content.

ECE 342–Jose Schutt Aine 1 ECE 442 Solid State Devices & Circuits 7. BJT Amplifiers Jose E. Schutt-Aine Electrical & Computer Engineering University of Illinois [email protected]ab.uiuc.edu

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
ECE 342–Jose Schutt Aine 2 Definitions – Used to increase the amplitude of an input signal to a desired level – This is a fundamental signal processing function – Must be linear (free of distortion) – Shape of signal preserved Amplifiers () , oi v t Av t where A is the voltage gain = v i (t) v o (t) AMP : o v i v Voltage Gain A v = : L p I Load Power P Power Gain A Input Power P =
ECE 342–Jose Schutt Aine 3 Amplifiers : pv i Note A A A = : o i i i Current Gain A i = oo p I I vi A = 20log V Voltage gain in dB A = I Current gain in dB A = 10log P Power gain in dB A = Expressing gain in dB (decibels)

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
ECE 342–Jose Schutt Aine 4 Amplifiers 11 2 2 DC P VI VI = + 100 L DC P Power Efficiency P η = Since output associated with the signal is larger than the input signal, power must come from DC supply DC I L dissipated P PPP + =+
ECE 342–Jose Schutt Aine 5 An amplifier has ± 10 V power supplies and an input current of 0.1 mA (sine wave) input voltage 1 V peak-to-peak and an output voltage with a peak of 9V. The load impedance is 1 k Ω and the amp draws 9.5 mA from each power supply. Determine: - the voltage gain - the current gain - the power gain - the power drawn from supplies - the power dissipated and η Problem 9 9 1 o v i V A V == = 9 ˆ 9 1 o I mA k Ω 20log 20log 9 19.1 vd B v A Ad B = ˆ 9 90 ˆ 0.1 o i i I A I = The current gain is

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
ECE 342–Jose Schutt Aine 6 Problem 40.5 810 0.05 d v I P A P == = 20log90 39.1 id B Ad B 99 40.5 22 Lo r m s o r m s Power at Load P V I mW −− = = 10 . 1 0.05 II r m s I r m s Power at input P V I mW = = 10log810 29.1 vd B B 10 9.5 10 9.5 190 dc P mW = dissipated dc I L P PP P = +− 190 0.05 4.05 149.6 dissipated Pm W =− = 100 21.3% L dc P P η =
ECE 342–Jose Schutt Aine 7 Biasing of Amp () IQ I I Vt V vt =+ Bias will provide quiescent points for input and output about which variations will take place. Bias maintain amplifier in active region.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 36

Lect_07 - ECE442 SolidStateDevices&Circuits 7.BJTAmplifiers...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online