U4083B Datasheet, PDF (4/16 Pages) TEMIC Semiconductors – Low-Power Audio Amplifier for Telephone Applications

3.3 Pin 4: Amplifier Input V_i, Pin 5: Amplifier Output 1 V_O1, Pin 8: Amplifier Output 2 V_O2
There are two identical operational amplifiers. Amplifier 1 has an open-loop gain ≥ 80 dB at
100Hz (Figure 8-2 on page 7), whereas the closed-loop gain is set by external resistors, R_f and
R_i (Figure 8-3 on page 8). The amplifier is unity gain stable, and has a unity gain frequency of
approximately 1.5 MHz. A closed-loop gain of 46 dB is recommended for a frequency range of
300Hz to 3400Hz (voice band). Amplifier 2 is internally set to a gain of –1.0 dB (0 dB). The out-
puts of both amplifiers are capable of sourcing and sinking a peak current of 200 mA. Output
voltage swing is between 0.4V and V_S – 1.3V at maximum current (Figure 8-18 on page 13 and
Figure 8-19 on page 13).
The output DC offset voltage between Pins 5 and 8 (V_O1 – V_O2) is mainly a function of the feed-
back resistor, R_f, because the input offset voltages of the two amplifiers neutralize each other.
Bias current of Amplifier 1 which is constant with respect to V_s, flows out of Pin 4 (V_i) and
through R_f, forcing V_O1 to shift negative by an amount equal to R_fI_IB and V_O2 positive to an equal
amount.
The output offset voltage specified in the electrical characteristics is measured with the feedback
resistor (R_f = 75 kΩ) shown in the typical application circuit, Figure 8-20 on page 14. It takes into
account the bias current as well as internal offset voltages of the amplifiers.
3.4 Pin 6: Supply and Power Dissipation
Power dissipation is shown in Figure 8-8 on page 9 to Figure 8-10 on page 10 for different loads.
Distortion characteristics are given in Figure 8-11 on page 10 to Figure 8-13 on page 11.
P_totmax
=
T_{----j--m----a--x----–-----}T_{----a--m----b-}
R_thJA
where
T_jmax = Junction temperature = 140°C
T_amb = Ambient temperature
R_thJA = Thermal resistance, junction-ambient
Power dissipated within the IC in a given application is found from the following equation:
P_tot = (V_S × I_S) + (I_RMS × V_S) – (R_L × I_RMS2)
I_S is obtained from Figure 8-15 on page 12.
I_RMS is the RMS current at the load R_L.
The IC's operating range is defined by a peak operating load current of ±200 mA (Figure 8-8 on
page 9 to Figure 8-13 on page 11). It is further specified with respect to different loads (see Fig-
ure 8-14 on page 12). The left (ascending) portion of each of the three curves is defined by the
power level at which 10% distortion occurs. The center flat portion of each curve is defined by
the maximum output current capability of the integrated circuit. The right (descending) portion of
each curve is defined by the maximum internal power dissipation of the IC at 25°C. At higher
ambient temperatures, the maximum load power must be reduced according to the above men-
tioned equation.
4 U4083B
4655C–CORD–03/06