Telecommunications – Transmitter – Power control – power supply – or bias voltage supply
Patent
1996-12-12
1999-07-06
Chin, Wellington
Telecommunications
Transmitter
Power control, power supply, or bias voltage supply
455126, 455 63, 455 673, 455296, H04M 732
Patent
active
059208082
ABSTRACT:
A biasing circuit for a power amplifier, for use in a transmitter, that substantially reduces distortion during key-up and thereby reduces key-up time. The power amplifier includes an output transistor and a bias circuit. The bias circuit is applied to all the class AB stages of the power amplifier. The bias circuit provides to the output transistor a first bias level during the preheat period and a second bias level during the transmit period. This first bias level is predetermined to cause the output transistor to reach the steady-state junction temperature achieved by the output transistor during the transmit period (i.e., when transmitting output signals biased with the second bias level). The preheat period ends when this steady-state temperature is reached. Thus, the power amplifier can then transition to a transmit period having already reached the steady-state junction temperature. Because the output transistor is already heated to the steady-state junction temperature, "thermal" distortion (i.e., the distortion incurred when the output transistor's junction temperature changes while transmitting) is avoided and the key-up time is reduced.
REFERENCES:
patent: 4317083 (1982-02-01), Boyd
patent: 4654672 (1987-03-01), Bailey et al.
patent: 5406225 (1995-04-01), Iida et al.
Deters Gerald D.
Frederick Thomas L.
Jones David E.
Murphy Kevin P.
Walker Mark A.
Chin Wellington
Ferguson Keith
Glenayre Electronics, Inc.
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