Microelectronic Circuits, Kyung Hee Univ. Spring, 2016 …tioh.weebly.com/uploads/2/5/4/3/25433593/1week_part_2.pdf · Microelectronic Circuits, Kyung Hee Univ. Spring, 2016 1 1.3

Microelectronic Circuits, Kyung Hee Univ. Spring, 2016

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1.3 Analog and Digital Signals

• Analog signal • Analogous to the presented physical signal

• Take on any value

• Continuous variation over its range of activity

• Vast majority of signals in the world

• Digital signal• Sequence of numbers

• Sampling: signal magnitude at an instant of time (discrete-time signal)

• Quantization(digitized, discretized, digitized): represent finite number of digits

Figure 1.8 Sampling the continuous-time analog signal in (a) results in the discrete-time signal in (b).


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• A sequence of numbers that represent the magnitudes of the successive signal samples

• Binary number system 𝐷 = 𝑏020 + 𝑏12

1 + 𝑏222 +⋯+ 𝑏𝑁−12

𝑁−1

• LSB: least significant bit / MSB: most significant bit

• Quantization error

• Analog-to-digital converter (A/D, ADC)

• Digital-to-analog converter (D/A, DAC)

Figure 1.9 Variation of a particular binary digital signal with time. Figure 1.10 Block-diagram representation of the analog-to-digital

converter (ADC).


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1.4 Amplifiers

• Signal amplification: the most fundamental signal-processing function

• Amplifier (as a circuit building block)

• Only consider external characteristics


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1.4.1 Signal Amplification

• Require signal amplification• Transducers provide weak signals (mV or mV)

• For reliable signal processing

→ Signal amplifier

• Linearity: output waveform must be identical to those in the input waveform except of course for having larger magnitude

• Any change in waveform = distortion

• 𝑣𝑜 𝑡 = 𝐴𝑣𝑖 𝑡

• A: amplifier gain

• Linear amplifier

• Voltage amplifier (preamplifier in the home stereo system)

• Power amplifier (provide only a modest amount of voltage gain but substantial current gain)


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1.4.2 Amplifier Circuit Symbol

• Two port network (Fig.1.11)

• Input and output ports and direction of signal flow

• The common terminal exists between the input and output ports (reference point, circuit ground)

Figure 1.11 (a) Circuit symbol for amplifier. (b) An amplifier with a common terminal (ground) between

the input and output ports.


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1.4.3 Voltage Gain

• 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 𝑔𝑎𝑖𝑛 (𝐴𝑣) ≡𝑣𝑜

𝑣𝐼

• Transfer characteristic of a linear amplifier


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1.4.4 Power Gain and Current Gain

• Transformer: deliver power to the load less than or at most equal supplied by the signal source

• Amplifier: deliver power to the load greater than that obtained from the signal source – power gain

• 𝑃𝑜𝑤𝑒𝑟 𝑔𝑎𝑖𝑛 𝐴𝑝 ≡𝑙𝑜𝑎𝑑 𝑝𝑜𝑤𝑒𝑟 (𝑃𝐿)

𝑖𝑛𝑝𝑢𝑡 𝑝𝑜𝑤𝑒𝑟 (𝑃𝐼)=

𝑣𝑜𝑖𝑜

𝑣𝐼𝑖𝐼

• 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 𝑔𝑎𝑖𝑛 𝐴𝑖 ≡𝑖𝑜

𝑖𝐼

• 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 𝑔𝑎𝑖𝑛 (𝐴𝑣) ≡𝑣𝑜

𝑣𝐼

• 𝐴𝑝 = 𝐴𝑣𝐴𝑖


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1.4.5 Expressing Gain in Decibels

• Ratios of similarly dimensioned quantities

• Dimensionless numbers (V/V, A/A, W/W)

• Express amplifier gain with a logarithmic measure

• 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 𝑔𝑎𝑖𝑛 𝑖𝑛 𝑑𝑒𝑐𝑖𝑏𝑒𝑙𝑠 = 20 log 𝐴𝑣 𝑑𝐵

• 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 𝑔𝑎𝑖𝑛 𝑖𝑛 𝑑𝑒𝑐𝑖𝑏𝑒𝑙𝑠 = 20 log 𝐴𝑖 𝑑𝐵

• 𝑃𝑜𝑤𝑒𝑟 𝑔𝑎𝑖𝑛 𝑖𝑛 𝑑𝑒𝑐𝑖𝑏𝑒𝑙𝑠 = 10 log 𝐴𝑝 𝑑𝐵

• Negative gain 𝐴𝑣: 180° phase difference between input and output signals (not attenuating)

• -20 dB: attenuating the input signal by a factor of 10 (𝐴𝑣 = 0.1 𝑉/𝑉)


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1.4.6 Amplifier Power Supplies

Figure 1.13 An amplifier that requires two dc supplies (shown as batteries) for operation.

• Power for the load is greater than the power from the signal source –Where the source of this additional power

• Amplifiers need dc power supplies for their operation

• Two dc sources: Positive 𝑉𝐶𝐶, negative 𝑉𝐸𝐸

• 𝑃𝑑𝑐 = 𝑉𝐶𝐶𝐼𝐶𝐶 + 𝑉𝐸𝐸𝐼𝐸𝐸

• 𝑃𝑑𝑐 + 𝑃𝐼 = 𝑃𝐿 + 𝑃𝑑𝑖𝑠𝑠𝑖𝑝𝑎𝑡𝑒𝑑

• Power efficiency 𝜂 ≡𝑃𝐿

𝑃𝑑𝑐× 100

• Some require only one

power supply


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1.4.7 Amplifier Saturation

• Linearity in amplifier transfer characteristic within a limited range of input and output voltages

• Positive and negative saturation levels: 𝐿+, 𝐿−• Within a fraction of a volt of the voltage of the corresponding power supply

• To avoid distorting the output signal, input signal swing within the linear range of operation

•𝐿−

𝐴𝑣≤ 𝑣𝐼 ≤

𝐿+

𝐴𝑣

• If lager, output was clipped off

Figure 1.14 An amplifier transfer characteristic that is linear except

for output saturation.


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1.4.8 Symbol Convention

• Total instantaneous quantity: 𝑖𝐶 𝑡 = 𝐼𝐶 + 𝑖𝑐(𝑡)

• 𝑖𝑐 𝑡 = 𝐼𝑐 sin𝜔𝑡

• dc power supplies: 𝑉𝐶𝐶

Figure 1.15 Symbol convention employed throughout the book.


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Homework

• Exercise 1.9, 1.10, 1.11

• Example 1.2

Documents

Microelectronic Circuits, Kyung Hee Univ. Spring, 2016 …tioh.weebly.com/uploads/2/5/4/3/25433593/1week_part_2.pdf · Microelectronic Circuits, Kyung Hee Univ. Spring, 2016 1 1.3