MAT04 Analog Devices, MAT04 Datasheet - Page 8

• Manufacturer Part Number: MAT04
• Description: Matched Monolithic Quad Transistor
• Manufacturer: Analog Devices

MAT04
LOW NOISE, HIGH SPEED INSTRUMENTATION
AMPLIFIER
The circuit of Figure 6 is a very low noise, high speed amplifier,
ideal for use in precision transducer and professional audio
applications. The performance of the amplifier is summarized in
Table I. Figure 7 shows the input referred spot noise over the
0–25 kHz bandwidth to be flat at 1.2 nV/√Hz. Figure 20 high-
lights the low 1/f noise corner at 2 Hz.
The circuit uses a high speed op amp, the OP17, preceded by
an input amplifier. This consists of a precision dual matched-
transistor, the MAT02, and a feedback V-to-I converter, the
MAT04. The arrangement of the MAT04 is known as a “linear-
ized cross quad” which performs the voltage-to-current conversion.
The OP17 acts as an overall nulling amplifier to complete the
feedback loop. Resistors R1, R2, and R3, R4 form voltage divid-
ers that attenuate the output voltage swing since the “cross
quad” arrangement has a limited input range. Biasing for the in-
put stage is set by Zener diode Z1. At low currents, the effective
zener voltage is about 3.3 V due to the soft knee characteristic of
the Zener diode. This results in a bias current of 530 µA per
side for the input stage. The gain of this amplifier with the val-
ues shown in Figure 6 is:
V
V
OUT
IN
=
33000
R
G
Input Noise
Voltage Density
Bandwidth
Slew Rate
Common-Mode Rejection G = 1000
Distortion
Settling Time
Power Consumption
Table I. Instrumentation Amplifier Characteristics
G = 1000
G = 100
G = 10
G = 500
G = 100
G = 10
G = 100
f = 20 Hz to 20 kHz
G = 1000
1.2 nV/√Hz
3.6 nV/√Hz
30 nV/√Hz
400 kHz
1 MHz
1.2 MHz
40 V/µs
130 dB
0.03%
10 µs
350 mW