AIC1863CD Просмотр технического описания (PDF) - Analog Intergrations

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AIC1863CD

IR Preamplifier for Remote Control System

Analog Intergrations 

AIC1863

n TYPICAL PERFORMANCE CHARACTERISTICS (Continued)

Pin 5 DC Voltage vs. Input DC Current

4

Ta=25°C

3

V CC=5V

2

1

00

2 0 40 60

80 100 120 140 160 180 200

Input DC Current (µA)

n APPLICATION INFORMATIONS

l THE OPERATION

AUTOMATIC BIAS LEVEL CONTROL

An ABLC (Automatic Bias Level Control) circuit is

built into the input section to prevent the input level

from being saturated by the external disturbing

lights, such that this circuit is actuated by a strong

external disturbing light to fix the bias level of the

input terminal.

TRANS-IMPEDANCE AMPLIFIER (T.I.A.)

The Trans-impedance amplifier is an inverted ampli-

fier with a sufficiently low input resistance, which

amplifies the input photocurrent pulses. The resis-

tance of the input at the signal frequency should

not be too high. Otherwise the wanted signal would

be lost to the junction capacitance of photodiode.

AUTO-GAIN CONTROL AMPLIFIER (A.G.C.)

The voltage gain of auto-gain control amplifier is

controlled by the voltage at CA pin. In so doing, it

supports the long-time interference suppression of

the evaluation circuit.

EVALUATION CIRCUIT

The signal delivered from the band-pass filter is

compared with a reference by the detector com-

parator. This reference is determined by the short-

time boost circuit and the long-time control circuit.

The inherent offset of the detector comparator and

the reference determine the sensitivity of the

evaluation circuit. The integrator is controlled by the

above mentioned comparison. Its output is used to

control the output stage after being processed

through a schmitt-trigger. Use of the integrator

keeps the output free of short-time interference.

The ground of the evaluation circuit is routed out

separately at pin 4, in order to minimize effect of

the output switching edges.

SHORT-TIME BOOST CIRCUIT (S.B.C.)

The short-time boost circuit reduces the sensitivity

of the evaluation circuit after reception of a signal.

This prevents short-time interference from affecting

the output. The reduction in sensitivity is achieved

by boosting the reference input of the detector

comparator.

LONG-TIME CONTROL CIRCUIT (L.C.C.)

The long-time control circuit improves the circuit’s

resistance to long-time interference by adapting the

sensitivity of the evaluation circuit and the amplifi-

cation of the AGC amplifier. Reduction of the

evaluation circuit sensitivity is thereby achieved in

the same way, as for the SBC, by raising the refer-

ence input of the detector comparator. The external

capacitor C1 is charged as long as the signal is

delivered from band pass filter and the voltage of C1

provides the necessary control voltage for AGC

amplifier.

6

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