UPC1678G-E2 Просмотр технического описания (PDF) - NEC => Renesas Technology
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UPC1678G-E2 Datasheet PDF : 16 Pages
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TEST CIRCUIT
VCC
1 800 pF
µPC1678G
8
50 Ω
IN
1
1 800 pF
L
50 Ω
5
OUT
1 800 pF
2, 3, 4, 6, 7
L: 20.5 T, 2 mm I.D., φ 0.25 UEW
(about 300 nH)
INDUCTOR FOR THE OUTPUT PIN
The internal output transistor of this IC consumes 30 mA, to output medium power. To supply current for output
transistor, connect an inductor between the VCC pin (pin 8) and output pin (pin 5).
The inductor has both DC and AC effects. In terms of DC, the inductor biases the output transistor with minimum
voltage drop to output enable high level. In terms of AC, the inductor make output-port impedance higher to get
enough gain. In this case, large inductance and Q is suitable.
CAPACITORS FOR THE VCC, INPUT AND OUTPUT PINS
Capacitors of 1 800 pF are recommendable as the bypass capacitor for the VCC pin and the coupling capacitors
for the input and output pins.
The bypass capacitor connected to the VCC pin is used to minimize ground impedance of VCC pin. So, stable bias
can be supplied against VCC fluctuation.
The coupling capacitors, connected to the input and output pins, are used to cut the DC and minimize RF serial
impedance. Their capacitance are therefore selected as lower impedance against a 50 Ω load. The capacitors thus
perform as high pass filters, suppressing low frequencies to DC.
To obtain a flat gain from 100 MHz upwards, 1 800 pF capacitors are used in the test circuit. In the case of under
100 MHz operation, increase the value of coupling capacitor such as 10 000 pF. Because the coupling capacitors
are determined by equation, C = 1/(2 πRfc).
Data Sheet P11491EJ4V0DS00
5
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