L01 May 301 EE 2303/001 Electronics I Summer 2001 Professor Ronald L. Carter

L01 May 302 Thevenin Equivalent Any two terminals of a circuit can be replaced by –the open circuit source voltage, V TH, in series with –the resistance, R TH, (impedance) obtained when all independent sources are set to zero. Voltage sources --> short circuit Current sources --> open circuit

L01 May 303 Norton Equivalent Any two terminals of a circuit can be replaced by –the short circuit source current, I N, in parallel with –the resistance, R N, (impedance) obtained when all independent sources are set to zero. Voltage sources --> short circuit Current sources --> open circuit

L01 May 304 Relationships and General Approach By definition, R TH = R N. V TH = I N R N, and I N = V TH /R TH If dependent sources are present, they cannot be set to zero, so –determine V TH or I N as before –apply a test potential or current to the terminals and solve for v test /i resp = R TH or v resp /i test = R TH

L01 May 305 Figure 1.17 Model of an electronic amplifier, including input resistance R i and output resistance R o.

L01 May 306 Figure 1.18 Source, amplifier model, and load for Example 1.1.

L01 May 307 Figure 1.19 Cascade connection of two amplifiers.

L01 May 308 Figure 1.20 Cascaded amplifiers of Example 1.2.

L01 May 309 Figure 1.21 Simplified model for the cascaded amplifiers of Figure See Example 1.3.

L01 May 3010 Figure 1.24 Amplifier of Example 1.4.

L01 May 3011 Figure 1.25 Current-amplifier model.

L01 May 3012 Figure 1.26 Voltage amplifier of Examples 1.5, 1.6, and 1.7.

L01 May 3013 Figure 1.27 Current-amplifier model equivalent to the voltage-amplifier model of Figure See Example 1.5.

L01 May 3014 Figure 1.28 Transconductance-amplifier model.

L01 May 3015 Figure 1.29 Transconductance amplifier equivalent of the voltage amplifier of Figure See Example 1.6.

L01 May 3016 Figure 1.30 Transresistance-amplifier model.

L01 May 3017 Figure 1.31 Transresistance amplifier that is equivalent to the voltage amplifier of Figure See Example 1.7.

L01 May 3018 Figure 1.32 If we want to sense the open-circuit voltage of a source, the amplifier should have a high input resistance, as in (a). To sense short-circuit current, low input resistance is called for, as in (b).

L01 May 3019 Figure 1.34 To avoid reflections, the amplifier input resistance R i should equal the characteristic resistance Z o of the transmission line.

L01 May 3020 Figure 1.37 Capacitive coupling prevents a dc input component from affecting the first stage, dc voltages in the first stage from reaching the second stage, and dc voltages in the second stage from reaching the load.

L01 May 3021 Figure 1.43 Differential amplifier with input sources.

L01 May 3022 Figure 1.44 The input sources v i1 and v i2 can be replaced by the equivalent sources v icm and v id.

L01 May 3023 Figure 1.46 Setup for measurement of common-mode gain.

L01 May 3024 Figure 1.47 Setup for measuring differential gain. A d = v o /v id.