TDK5111 Просмотр технического описания (PDF) - Infineon Technologies
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TDK5111 Datasheet PDF : 39 Pages
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TDK 5111
Applications
The output power Po is reduced by operating in an “overcritical” mode
characterised by RL > RLC.
The power efficiency (and the bandwidth) increase when operating at a slightly
higher RL, as shown in Figure 4-7.
The collector efficiency E is defined as
E=
P
O
VS IC
The diagram of Figure 4-7 was measured directly at the PA-output at VS = 3 V.
Losses in the matching circuitry decrease the output power by about 1.5 dB. As
can be seen from the diagram, 250 Ω is the optimum impedance for operation
at 3 V. For an approximation of ROPT and POUT at other supply voltages those
2 formulas can be used:
ROPT ~ VS
and
POUT ~ ROPT
18
16
14
12
10
8
6
4
2
0
0
Pout [mW]
10*Ec
100
200
300
400
500
RL [Ohm]
Figure 4-7
Power_E_vs_RL.wmf
Output power Po (mW) and collector efficiency E vs. load resistor RL.
The DC collector current Ic of the power amplifier and the RF output power Po
vary with the load resistor RL. This is typical for overcritical operation of class C
amplifiers. The collector current will show a characteristic dip at the resonance
frequency for this type of “overcritical” operation. The depth of this dip will
increase with higher values of RL.
Wireless Components
4 - 10
Specification, October 2002
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