晶体管频率特性
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出现下降趋势是由于有效基区
T
T
C r f f C r 2284πωω=
1
111a b S =输出端恰当置端条件下的
2007 Semiconductor Device Electronics
(Agilent)HP8510 series network analyzer 张万荣2007 Semiconductor Device Electronics
举例—实测微波SiGe HBT 张万荣2007 Semiconductor Device Electronics
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寄生或分布参数也影响特征频率f T 和最高振荡频率管壳和封装，极间电容，键合电容，杂散电容，延伸电极形MOS 电容(现代微波管它占总C
的50~75%)C
e T E bb T
m C L f R r f f )(8'2
ππ++=
张万荣
张万荣2007 Semiconductor Device Electronics
白噪声区2007 Semiconductor Device Electronics
(2)若f>>f CH C/V T=g m,
n f
2007 Semiconductor Device Electronics
2007 Semiconductor Device Electronics
2007 Semiconductor Device Electronics 2007 Semiconductor Device Electronics
2007 Semiconductor Device Electronics E
C
E
B 张万荣2007 Semiconductor Device Electronics
2007 Semiconductor Device Electronics
张万荣2007 Semiconductor Device Electronics
–Cross section of a millimetre-wave III-V HEMT device. Current flows from the source to the drain in the high mobility buried channel under the Schottky gate contact. The gate sits in a recess to improve the current modulation in the device.