AS2333

Document number: DS42770 Rev. 3 - 2

8 of 16

www.diodes.com

January 2021

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AS2333

Application Information

Overview

The AS2333 is low-power, zero-drift, high-precision, rail-to-rail input and output operational amplifier, which adopts chopper-stabilized function

circuits to provide the advantage of minimizing input offset voltage and offset voltage drift over time and temperature. Its input common-mode

voltage range extends 0.1V beyond the supply rails to allow for sensing near ground or system VDD. The device operates from a single-supply

voltage as low as 1.8V, is unity-gain stable, has no 1/f noise, and has good PSRR and CMRR performance. These features make the AS2333

suitable for a wide range of general-purpose applications, especially for low-power and high-precision applications.

Low Input Referred Noise

The device AS2333 is chopper-stabilized amplifier, which greatly reduces the flicker noise. The zero-drift chopper-stabilized amplifiers are

especially suited for accurate, high-gain amplification at lower frequencies. In general, they do not exhibit the higher bandwidth of linear

operational amplifiers, and the location of their clock frequency establishes a practical frequency limit on signal fidelity. This makes performance at

low frequencies especially important, and the chopper-stabilized architecture further contributes to low-frequency usefulness by eliminating the

classic linear operational amplifier 1/f input voltage noise. Many high-gain sensor applications are at low frequencies, making zero-drift amplifiers a

natural choice for this function.

The below graphs compare the voltage noise density behaviors of conventional amplifiers and zero-drift amplifiers. The 1/f noise elimination in

zero-drift amplifiers allow the AS2333 to have much lower noise at DC and low frequencies compared to the conventional low-noise amplifiers.

100

1k

10k

1n

10n

100n

1μ

V

CC = 5.0V, VEE = 0V, AV = 1

Frequency (Hz)

100

1k

10k

1

10

100

1000

Frequency (Hz)

Figure 1. Input Voltage Noise in Conventional Amplifier (AZV832)

Figure 2. Input Voltage Noise in Zero-Drift Amplifier (AS2333)

Driving a Capacitive Load

The AS2333 can directly drive 200pF in unity-gain without oscillation. The unity-gain follower is the most sensitive configuration to capacitive

loading. Capacitive loading directly on the output terminal can decrease the device’s phase margin, leading to high-frequency ringing or oscillation.

To drive a heavier capacitive load, the circuit in Figure 3 can be used. The resistor RNULL and CL form a pole to increase stability by adding more

phase margin to the system. The bigger the RNULL resistor value, the more stable VOUT is. Figure 4 and Figure 5 show the AS2333’s output pulse

response waveforms with and without RNULL 330Ω for load conditions CL = 470pF and RL = 10kΩ.

1μ