Datasheet AS2333 (Diodes) - 7

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, has good PSRR and CMRR performance. These features make the part suitable for a wide range of general-purpose applications, especially for low-power high precision applications.
Low Input Referred Noise
The device AS2333 is chopper stabilized amplifier, the flicker noise is reduced greatly because of this technique. 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 amplifier, 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. Below plots compared conventional amplifier voltage noise density behavior and zero-drift amplifier’s, this 1/f noise elimination in zero-drift amplifier allows the AS2333 to have much lower noise at DC and low frequency compared to conventional low noise amplifier. 1000 1μ V = 5.0V, V = 0V, A = 1 z) CC EE V H V/ z) (n H y t si 100 100n (V/ n e ise D o l N ra e ct g e lta Sp 10n 10 t Vo sei u o p N In e g atl Vo 1n 1 100 1k 10k 100 1k 10k Frequency (Hz) Frequ ency (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 RNULL resistor value the more stable VOUT is. Figure 4 and Figure 5 are AS2333 output pulse response waveforms with and without RNULL 330Ω for load conditions CL = 470pF and RL = 10kΩ. AS2333 7 of 14 June 2020 Document number: DS42770 Rev. 2 - 2
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