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RF Electronics Chapter 8: Amplifiers: Stability, Noise and Gain Page 279 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. 2 1 22 21 12 11 2 1 V V S S S S V V Eqn. 8.3 0 2 1 1 11 V V V S i.e. reflection coefficient at port 1, with port 2 matched. 0 1 2 2 22 V V V S i.e. reflection coefficient at port 2, with port 1 matched. 0 2 1 2 21 V V V S i.e forward gain, with port 2 matched. 0 1 2 1 12 V V V S i.e reverse gain, with port 1 matched. An amplifier is unilateral if S 12 = 0, i.e. the reverse gain is zero. That applies to many amplifiers, particularly operational amplifiers and other ICs where the output is well separated from the input. The input reflection coefficient is: load load in S S S S 22 21 12 11 1 For a unilateral amplifier 11 S in Eqn. 8.4 source source out S S S S 11 12 21 22 1 For a unilateral amplifier 22 S out Eqn. 8.5 The Available Power Gain (G A ) is the ratio of the maximum available power at the load to the maximum available power at the source. It is the amplifier gain under ideal conditions as it assumes conjugate input and output matching. G A is defined as: ) 1 ( 1 ) 1 ( 2 2 11 2 2 21 out source source A S S source from available Power network from available Power G Eqn. 8.6 The Transducer Power Gain (G T ) is the ratio of the actual power at the load to the maximum available power at the source. It is the amplifier gain under actual load conditions. It assumes a conjugate input match, but uses the actual output match. G T is defined as: 2 22 2 2 2 2 21 1 1 ) 1 )( 1 ( load in source load source T S S source from available Power load the to delivered Power G Eqn. 8.7 There are measurement functions for G A and G T in Cadence AWR DE. Under ideal conditions, source = 0 and load = 0 so that 2 21 S G G T A Eqn. 8.8 An amplifier includes input and output matching circuits as shown in figure 8.5. The input match provides maximum power when in = source * so that the gain of the input matching network is G S = 1. Similar when the output has a conjugate match so that out = load *, then G L =1. RF Electronics: Design and Simulation 279 www.cadence.com/go/awr