The IC T2525 is a complete IR receiver for data communication developed and optimized for use in carrier-frequency-modulated transmission applications. Its function can be described using the block diagram (see Figure 1). The input stage meets two main functions. First, it provides a suitable bias voltage for the PIN diode. Secondly, the pulsed photo-current signals are transformed into a voltage by a special circuit which is optimized for low-noise applications. After amplification by a Controlled Gain Amplifier (CGA), the signals have to pass a tuned integrated narrow bandpass filter with a center frequency f0 which is equivalent to the chosen carrier frequency of the input signal. The demodulator is used to convert the input burst signal into a digital envelope output pulse and to evaluate the signal information quality, i.e., unwanted pulses will be suppressed at the output pin. All this is done by means of an integrated dynamic feedback circuit which varies the gain as a function of the present environmental condition (ambient light, modulated lamps etc.). Other special features are used to adapt to the current application to secure best transmission quality. The T2525 operates in a supply-voltage range of 4.5 V to 5.5 V. Figure 1. Block Diagram