RX3310A
FUNCTION DESCRIPTION
RF AMPLIFIER
The RF amplifier uses a common emitter configuration with a separate emitter connection (VEE). The input signal (VIRF)
should be ac-coupled externally. The output of the amplifier is open collector so that the gain may be set with an external
tuned load.
MIXER
The mixer is doubly-balanced configuration and has an ac-coupled input.
OSCILLATOR
A balanced oscillator configuration is used with an L-C tank externally connected across the OSC1 and OSC2 pins. The
frequency of the oscillator is determined by the external capacitor, C1, and inductor, L1 (please refer to application circuit
schematic).
IF AMPLIFIER
The IF amplifier is a differential input, single-ended output emitter-coupled pair. It is used to provide additional gain in
order to reduce the influence of the noise of the succeeding limiter amplifier on the total receiver noise figure.
IF FILTER
To minimize external component costs, an active IF filter is fully integrated.
LIMITER
The limiting amplifier consists of several dc-coupled amplifier stages and outputs an RSSI signal.
COMPARATOR
Following the limiting amplifier, the RSSI signal is passed through an additional buffer stage and is then fed to the
comparator's positive and negative terminals, which possess different R-C filter time constants. A larger off-chip
capacitor is used at the negative comparator input and hence, its terminal voltage represents the average value of the
RSSI signal. A smaller off-chip capacitor is used at the positive comparator input and this allows the positive input to
follow the RSSI signal instantaneously. When the received RSSI signal exceeds its average value (when an ASK on
signal is received), the comparator output is switched on.
BAND GAP REFERENCE
A band gap reference provides precise biasing of the entire chip over temperature.
V2.0
6
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