Datasheet MAT04 (Analog Devices) - 8

MAT04
Figure 5. Vector Summer
LOW NOISE, HIGH SPEED INSTRUMENTATION Table I. Instrumentation Amplifier Characteristics AMPLIFIER
The circuit of Figure 6 is a very low noise, high speed amplifier, Input Noise G = 1000 1.2 nV/√Hz ideal for use in precision transducer and professional audio Voltage Density G = 100 3.6 nV/√Hz applications. The performance of the amplifier is summarized in G = 10 30 nV/√Hz Table I. Figure 7 shows the input referred spot noise over the Bandwidth G = 500 400 kHz 0–25 kHz bandwidth to be flat at 1.2 nV/√Hz. Figure 20 high- G = 100 1 MHz lights the low 1/f noise corner at 2 Hz. G = 10 1.2 MHz The circuit uses a high speed op amp, the OP17, preceded by an input amplifier. This consists of a precision dual matched- Slew Rate 40 V/µs transistor, the MAT02, and a feedback V-to-I converter, the Common-Mode Rejection G = 1000 130 dB MAT04. The arrangement of the MAT04 is known as a “linear- ized cross quad” which performs the voltage-to-current conversion. Distortion G = 100 The OP17 acts as an overall nulling amplifier to complete the f = 20 Hz to 20 kHz 0.03% feedback loop. Resistors R1, R2, and R3, R4 form voltage divid- ers that attenuate the output voltage swing since the “cross Settling Time G = 1000 10 µs quad” arrangement has a limited input range. Biasing for the in- Power Consumption 350 mW 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: VOUT = 33000 VIN RG –8– REV. D