Philips Semiconductors
Low voltage versatile telephone transmission circuit
with dialler interface and transmit level dynamic limiting
Product specification
TEA1064B
Receiving amplifier IR, QR+, QR− and GAR
The receiving amplifier has one input IR and two
complimentary outputs, QR+ (non-inverting) and QR−
(inverting). These outputs may be used for single-ended or
differential drive, depending on the type and sensitivity of
the earpiece used (see Fig.13). Gain from IR to QR+ is
typically 31 dB with R4 = 100 kΩ, sufficient for
low-impedance magnetic or dynamic earpieces which are
suitable for single-ended drive. By using both outputs
(differential drive) the gain is increased by 6 dB.
Differential drive can be used when the earpiece
impedance exceeds 450 Ω as with high-impedance
dynamic, magnetic or piezo-electric earpieces.
handbook, full pagewidth
QR+
5
4 QR−
11 VEE
(a)
QR+
5
4 QR−
(b)
QR+ (1)
5
4 QR−
(c)
QR+ (2)
5
4 QR−
MBA441
(d)
Resistor (1) may be connected to prevent distortion (inductive load).
Resistor (2) is required to increase the phase margin (stability with capacitive load).
Fig.13 Alternative receiver arrangements (a) dynamic earpiece with an impedance less than 450 Ω
(b) dynamic earpiece with an impedance more than 450 Ω
(c) magnetic earpiece with an impedance more than 450 Ω
(d) piezo-electric earpiece.
March 1994
12