High Linearity
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=77GHz.
(2)
For PA of CDMA, High Linearity
Applications:
BVceo~14V, BVcbo=23V, BVebo=7V, DC
gain=63
fT=50Ghz, fmax=77Ghz
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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 = 26 mA
with Vce = 3 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
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*
VCE = 3.5 V, IC = 4 mA,
* P1dB,out = 16.2 dBm
* PAE @ 1dB = 51.8 %,
* Linear Gain = 24 dB
* IMD3 @ I dB = -20.7 dBc, IP3 = 34 dBm
* IP3 - P1dB = 17.8 dB
Fig.3
Power characteristics of 2 x 20 um2 x 2-finger device
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