MAT04FPZ Analog Devices Inc, MAT04FPZ Datasheet - Page 10

• Manufacturer Part Number: MAT04FPZ
• Description: IC TX MATCHED MONO QUAD 14-DIP
• Manufacturer: Analog Devices Inc

Specifications of MAT04FPZ

• Transistor Type: 4 NPN (Quad)
• Current - Collector (ic) (max): 30mA
• Voltage - Collector Emitter Breakdown (max): 40V
• Vce Saturation (max) @ Ib, Ic: 60mV @ 100µA, 1mA
• Current - Collector Cutoff (max): 5nA
• Power - Max: 350mW
• Frequency - Transition: 300MHz
• Mounting Type: Through Hole
• Package / Case: 14-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Dc Current Gain (hfe) (min) @ Ic, Vce: -

MAT04
VOLTAGE-CONTROLLED ATTENUATOR
The voltage-controlled attenuator (VCA) of Figure 9, widely
used in professional audio circles, can easily be implemented
using a MAT04. The excellent matching characteristics of the
MAT04 enables the VCA to have a distortion level of under
0.03% over a wide range of control voltages. The VCA accepts a
3 V RMS input and easily handles the full 20 Hz–20 kHz audio
bandwidth as shown in Figure 10. Noise level for the VCA is
more than 110 dB below maximum output.
In the voltage controlled attenuator, the input signal modulates
the stage current of each differential pair. Op amps A2 and A3
in conjunction with transistors Q5 and Q6 form voltage-to-current
converters that transform a single input voltage into differential
currents which form the stage currents of each differential pair.
The control voltage shifts the current between each side of the
two differential pairs, regulating the signal level reaching the
output stage which consists of op amp A1. Figure 11 shows the
increase in signal attenuation as the control voltage becomes
more negative.
The ideal transfer function for the voltage-controlled
attenuator is:
Where k = Boltzman constant 1.38 × 10
From the transfer function it can be seen that the maxi-
mum gain of the circuit is 2 (6 dB).
To ensure best performance, resistors R2 through R7 should
be 1% metal film resistors. Since capacitor C2 can see small
amounts of reverse bias when the control voltage is positive, it
may be prudent to use a nonpolarized tantalum capacitor.
V
OUT
T = temperature in °K
q = electronic charge = 1.602 × 10
/
IN
=
1
+
exp (



V
CONTROL
)



2
R
13
R
+
14
–23
R
–19
14
J/°K
C






kT
q





