1. ESE 232 Introduction to Electronic Circuits Professor Paul Min psm@wustl.edu (314) 853-6200 Bryan Hall 302A

2. Chapter 1. Signals and Amplifiers

3. Copyright  2004 by Oxford University Press, Inc. Microelectronics Integrated circuit technology Billions of components Typically implement in silicon wafer < 100 mm 2 Examples: microprocessors, memories, logic chips ESE 232 Study of microelectronics Analysis and design Functional circuits

4. Copyright  2004 by Oxford University Press, Inc. Electrical circuits Processes signals Driven by power sources (voltage or current) At every point in a circuit, voltage and current are defined. Signal (or power) represented in voltage (Thevenin form) Signal (or power) represented in current (Norton form) Equivalent and translatable v s (t) = R s i s (t)

5. Copyright  2004 by Oxford University Press, Inc. Signals Contain time-varying information. Exist in various forms (mechanical, electrical, chemical, acoustical, etc.) Can be conveniently processed by electrical circuits. Converting non-electrical signal to electrical signal is done by transducer (or sensor).

6. Copyright  2004 by Oxford University Press, Inc. Frequency Spectrum of Signals Often difficult to express signals in time (in mathematical form). Signals can be shown in frequency spectrum: Fourier series, Fourier transform, Z-transform, etc. → At what frequencies does the signal contain energy and by how much?

7. Copyright  2004 by Oxford University Press, Inc. Fourier Series Example: sine-wave v a (t) = V a sin wt v a (t) has all its energy at the angular frequency of w = 2πf. f is frequency in Hz. T = 1/f is period in seconds. Magnitude of this sine-wave at the angular frequency w is V a.

8. Copyright  2004 by Oxford University Press, Inc. Example: square-wave Time expression Frequency expression w 0 = 2π/T

9. Copyright  2004 by Oxford University Press, Inc. Frequency Allocations in the U.S.A.

10. Copyright  2004 by Oxford University Press, Inc. Digital v. Analog Analog signal: continuous value, continuous time Digital signal: discrete value, discrete time SampleQuantize Analog Signal Digital Signal Continuous time Continuous value Discrete time Continuous value Discrete time Discrete value

11. Copyright  2004 by Oxford University Press, Inc. Why Digital? Less expensive circuits Privacy and security Small signals (less power) Converged multimedia Error correction and reduction Why Not Digital? More bandwidth Synchronization in electrical circuits Approximated information

12. Copyright  2004 by Oxford University Press, Inc. Notation Total instantaneous quantities: lowercase symbols with uppercase subscripts (e.g., i C ) dc quantities: uppercase symbols with upper case subscripts (e.g., I C ) Power supply voltages: uppercase V’s with double letter uppercase subscripts (e.g., V EE ) dc currents draw from power supply: uppercase I’s with double letter uppercase subscripts (e.g., I CC ) Incremental signal quantities: lowercase symbols with lower case subscripts (e.g., i c )

13. Copyright  2004 by Oxford University Press, Inc. Amplifiers Amplification of input signal Linear amplifier: v o (t) = Av i (t) (A: constant gain) Voltage amplifier: changes input signal amplitude A v = voltage gain = v o / v i Preamplifier: shaping in frequency (i.e., amplifies different frequency components differently). Power amplifier: gains in voltage and current symbols

14. Copyright  2004 by Oxford University Press, Inc. Transfer Characteristic

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16. Power Supplies

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18. Amplifier Saturation maximum output minimum output

19. Copyright  2004 by Oxford University Press, Inc. Nonlinear Transfer Characteristics and Biasing To avoid saturation, input signal should be shifted. → Biasing Input signals are biased to operate in the middle of linear region.

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21. Circuit Models for Voltage Amplifiers

22. Copyright  2004 by Oxford University Press, Inc. High R i with gain 10 (Signal may be small.) Modest R i with gain 100 (Provide gain.) Small R i with gain 1 (Buffer output for next stage.)

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25. BJT

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30. Low pass RC circuit No distortion means constant amplitude gain and linear phase shift.

31. Copyright  2004 by Oxford University Press, Inc. High pass RC circuit No distortion means constant amplitude gain and linear phase shift.

32. Copyright  2004 by Oxford University Press, Inc. constantFunction of s

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35. Logic Inverter Circuit symbol input 1 (high) → out put 0 (low) input 0 (low) → out put 1 (high) Transfer function high v i (> 0.690V) → low v o (≈ 0.3V) low v i (≈ 0V) → high v o (≈ V DD ) linear region for mid value of v i Linear region for ordinary amplifier operation (transition region) Nonlinear (saturation) region for digital binary logic operation

36. Copyright  2004 by Oxford University Press, Inc. Noise Margin For cascaded inverters Noise margin for high input NM H = V OH - V IH Noise margin for low input NM L = V IL - V OL

37. Copyright  2004 by Oxford University Press, Inc. Ideal Inverter NM H = NM L =V DD / 2

38. Copyright  2004 by Oxford University Press, Inc. Abstract Implementation of Inverter voltage controlled switch. When v I is low, switch is open, leaving the vertical path disconnected. → v o = V DD is an open circuit voltage. When v I is high, switch connects the vertical path. → v o is a low level voltage determined largely by V offset, a characteristic of the voltage controlled switch. (R on is typically small.)

39. Copyright  2004 by Oxford University Press, Inc. Propagation Delay Change of output after input change is not instantaneous. Internal capacitance of devices causes the delay.

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