| 摘要 |
<p>A power-conserving, linear and broad band RF amplifier (200), suitable for use at more than one band in the ultra-high frequency regions allotted to radiotelephone transceivers, employs an emitter-follower output transistor (B3) to deliver the nominal 1.0 milliwatt RF power to a single-ended load (L) from a low voltage battery (Vcc), typically 2.7 v. dc, without the use of output coupling transformers. The amplifier receives only a small differential input signal (e.f) from a preceding mixer or multiplier stage having a typical peak-to-peak magnitude of 0.3 v. The differential input signal is applied to the emitters of a pair of transistors (B5, B6) whose bases are interconnected, one transistor of which (B6) is diode-connected in a current-mirror configuration and the other (B5) of which is configured in a common-base connection with emitter degeneration. The signals are summed at the collector of the common-base transistor (B5) to deliver a substantial voltage swing, illustratively 1.7 volts peak to peak, which is large enough to drive the base of the emitter-follower output transistor (B3) without requiring the high standby current in the emitter-follower normally required to maintain an emitter-follower in Class A operation. <IMAGE></p> |
