TEA1045

The TEA1045 is one kind of bipolar integrated circuit specially designed for use in a telephone subset to amplify the output from the handset microphone to the telephone line and to amplify the incoming speech on the line to the earpiece transducer.The microphone and earpoece transducers can be of the same type and construction.The overall characteristics of the TEA1045 are very well defined and controlled.Both send and receive gains within the integrated circuit have only a small overall spread of 4 dB(+/-26% about nominal).With line impedance and set-gain resistors closely controlled the performance of the subset is well defined in the system.

Features of the TEA1045 are:(1)automatic compensation of line losses by using a gain-controlled amplifier;(2)very accurate send,receive and VF(voice frequency) gains to achieve optimum system performance;(3)low supply current obtained entirely from a small proportion of the line current;(4)cancellation circuit to achieve required reduction in sidetone;(5)balanced microphone input circuit for reduced sidetone;(6)operation can be achieved if the subsets are paralleled;(7)stsbilised D.C. output for powering external VF oscillator;(8)send,VF and recevie gains can be preset externally by choice of resistors;(9)both low and high frequency characteristics of the send gain can be separately adjusted by external capacitors;(10)control of quiescent operating point on curve relating D.C. line current with amplifier gain.