High linearity is the most important power amplifier specification
in 3G WCDMA, WLAN applications. High intermod efficiency (intermod
efficiency is a measure of how efficiently the amplifier’s DC input
power is used to create linear amplification) is also extremely important,
especially in battery powered hand held applications.
High Linearity HBTs (HL) are basically designed to achieve good linearity
characteristics.
One significant parameter of the HBTs for CDMA PAM is IP3-P1dB value
where 2 finger, 2x20(HL) devices show 17.8dB, which is excellent for
CDMA PAM requirements. Frequency performance of HL devices also has
outstanding performance of fT>50GHz, fmax>80GHz.
For PA of WCDMA, WLAN, etc. High Linearity Applications
:BVceo > 13 V, fT > 50 GHz, fmax > 80GHz, DC gain = ~110
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Fig.1
Common emitter short circuit current
gain (H21) and unilateral power gain (U) of
2 x 20 um2 x 2-finger device at Ic = 20 mA
with Vce = 1.5 V |
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Fig.2
Dependence of current gain cut-off
frequency (fT) and maximum oscillation
frequency (fMax) on collector current of
2 x 20 um2 x 2-finger device
> VCE = 3.5 V, IC = 35 mA
> Frequency = 1.8 GHz
> P1dB,out = 16.1 dBm
> PAE @ 1dB = 34.3 %,
> Linear Gain = 24.2 dB
> IP3 = 27.5 dBm
> IP3 - P1dB@per tone = 15 dB |
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Fig.3
Power characteristics of 2 x 20 um2 x 2-finger device
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