子計畫八：HBT 中頻積體電路及後製程研究(3/3)

In this project, the realization of
matched impedance wideband amplifiers
fabricated by InGaP/GaAs hetero-junction
bipolar transistor (HBTs) process is reported.
The technique of multiple feedback loops
was used to achieve terminal impedance
matching and wide bandwidth at the same
time. A general method for the determination
of frequency responses of input/output return
losses (or S11/S22) from the poles of voltage
gain was also proposed. The experimental
results showed that a small signal gain of
16dB and a 3-dB bandwidth of 11.6GHz with
in-band input/output return loss less
than –10dB were obtained. These values
agreed well with those predicted from the
analytic expressions that we derived for
voltage gain, transimpedance gain,
bandwidth, input and output impedances.
Also these results are suited for the
specification of this project. The intrinsic
over-damped characteristic of this amplifier
was proved and emitter capacitive peaking
was used to remedy this problem. The
tradeoff between the input impedance
matching and bandwidth was also found.