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UPC8120T

VARIABLE GAIN AMPLIFIER SILICON MMIC FOR TRANSMITTER AGC OF DIGITAL CELLULAR TELEPHONE

NEC => Renesas Technology 

µPC8119T, µPC8120T

APPLICATION for µPC8119T, µPC8120T

1. TO GET MINIMUM GAIN

–1. VCC line filtering

A low pass filter must be attached to VCC line in order to suppress RF input leakage to VCC. (The low pass

filter: for example π type.) This filter must be inserted between VCC pin and matching inductor. If the low

pass filter is not attached to this point, minimum output level would not go down under the leakage level.

For example, µPC8119T’s RF input leakage level to VCC shows –30 dBm at 950 MHz and –17 dBm at 1440

dBm.

π type low pass filter constant example

Pattern L = 5 to 6 nH, C5 = C6 = 1000 pF (Refer to TEST CIRCUIT1, 2 and APPLICATION CIRCUIT

EXAMPLE)

In the case of testing on ‘µPC8119/20T TYPE2’ board, monitor the input leakage to VCC pin through ‘VCC

monitor line’ and adjust parallel capacitors to suppress leakage.

–2. Capacitor feed-back between VAGC and VCC pins

Feed-back capacitor between VAGC and VCC pins must be externally attached in order to decrease

impedance difference.

2. TO GET MAXIMUM GAIN

–1. Output matching

As for external matching circuit, only output port should be equipped in order to get maximum gain. Output

port matching in accordance with impedance of these ICs and next stage must keep the points as follows;

<1> AC points

• IC output impedance at maximum gain must be used.

• Inductance of L must be chosen to get S22 ~ –20 dBm at maximum gain.

<2> DC point

• On LC matching, L of low DC resistance must be chosen to apply voltage as same as VCC to output

pin.

3. OTHERS

–1. Input connection

Input port does not need to match externally. These ICs can be connected to front stage through coupling

capacitor (eg 1000 pF) for DC cut.

–2. VCC ON/OFF while voltage applied to VAGC

Due to internal transistor’s voltage rating, ON/OFF can be controlled with VCC voltage while 3.0 V or less is

applied to VAGC.

For the usage and application of µPC8119T and µPC8120T, please refer to the application note (Document

No. P12763E).

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