SA602A

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© NXP Semiconductors N.V. 2014. All rights reserved.

Product data sheet

Rev. 3 — 27 May 2014

4 of 19

NXP Semiconductors

SA602A

Double-balanced mixer and oscillator

7.

Functional description

The SA602A is a Gilbert cell, an oscillator/buffer, and a temperature-compensated bias

network as shown in Figure 3. The Gilbert cell is a differential amplifier (IN_A and IN_B

pins) that drives a balanced switching cell. The differential input stage provides gain and

determines the noise figure and signal handling performance of the system.

The SA602A is designed for optimum low-power performance. When used with the

SA604A as a 45 MHz cellular radio second IF and demodulator, the SA602A is capable of

receiving

119 dBm signals with a 12 dB S/N ratio. Third-order intercept is typically

13 dBm (that is approximately +5 dBm output intercept because of the RF gain). The

system designer must be cognizant of this large signal limitation. When designing LANs or

other closed systems where transmission levels are high, and small-signal or

signal-to-noise issues are not critical, the input to the SA602A should be appropriately

scaled.

Besides excellent low-power performance well into VHF, the SA602A is designed to be

flexible. The input, RF mixer output and oscillator ports support various configurations

provided the designer understands certain constraints, which are explained here.

The RF inputs (IN_A and IN_B pins) are biased internally. They are symmetrical. The

equivalent AC input impedance is approximately 1.5 k

 3 pF through 50 MHz. IN_A and

IN_B pins can be used interchangeably, but they should not be DC biased externally.

Figure 4 shows three typical input configurations.

Fig 3.

Equivalent circuit

aaa-013205

18 kΩ

25 kΩ

buffer

6

7

BIAS

1.5 kΩ

4

1.5 kΩ

5

BIAS

1

1.5 kΩ

3

GND

1.5 kΩ

BIAS

2