ADA4510-2ARZ-R7 datasheet(24/32 Pages) AD

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Data Sheet

ADA4510-2

THEORY OF OPERATION

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Figure 78. Simplified Schematic

The ADA4510-2 is a dual-channel, low-power, rail-to-rail input and

output, precision CMOS op amp that operates over a wide supply

voltage range of 6 V to 40 V. This amplifier uses the Analog

Devices DigiTrim technique to achieve a higher degree of precision

compared to previous CMOS amplifiers. The DigiTrim technique is

a method of trimming the offset voltage and the offset voltage tem-

perature drift of an amplifier after assembly. This technique corrects

any offset voltages and drifts caused by mechanical stresses during

assembly.

INPUT AND GAIN STAGES

Figure 78 shows the simplified circuit diagram for the ADA4510-2.

The input architecture provides high-impedance, rail-to-rail differ-

ential and common-mode input swing, low noise, low input bias

current, and low offset voltage.

An integrated EMI filter increases the signal robustness and helps

prevent EMI signals from coupling into the amplifier. Depending on

the input common-mode voltage, either the negative channel metal-

oxide semiconductor (NMOS) or the positive channel metal-oxide

semiconductor (PMOS) input stage can be active at any time. The

low offset voltage and low offset voltage drift specifications are

possible by using the DigiTrim technique on both the NMOS and

PMOS input stages.

The ADA4510-2 includes circuitry that extends the linear input

range, providing higher slew rates than a traditional input differential

pair and improving the THD. The wide gain bandwidth product of

10.4 MHz is achieved through internal Miller compensation.

OUTPUT STAGE

The output of the ADA4510-2 swings rail-to-rail to within 100 mV

of either supply rail. A capacitive load compensation block senses

the load capacitor and adds additional phase margin, if required,

to drive a large capacitor (at least 1 nF) and maintain amplifier

stability.

EMI REJECTION

High-frequency EMI is a threat to precision amplifier performance

in an intended application. Op amps must accurately amplify input

signals despite low signal strength and long transmission lines. All

operational amplifier pins are susceptible to EMI signals. These

high-frequency signals are coupled into an operational amplifier by

various means, such as conduction, near-field radiation, or far-field

radiation. For example, wires and printed circuit board (PCB) traces

act as antennas to pick up high-frequency EMI signals.

Op amps do not amplify EMI or RF signals due to the relatively low

bandwidth of the amplifier. However, due to the nonlinearities of the

input devices, op amps can rectify these out-of-band signals, which

then appear as a DC offset at the output.

The ADA4510-2 is designed with integrated EMI filters at the input

stage of the op amp. The EMIRR describes the ability of the

ADA4510-2 to perform as intended in the presence of electromag-

netic energy. The EMIRR is specified for the noninverting pin in

Table 1. A mathematical method of measuring EMIRR is defined as

follows:

EMIRR=20 log× ΔVIN_PEAK/ΔVOS

EMIRR performance of ADA4510-2 is shown in Figure 41.

NO PHASE INVERSION

The ADA4510-2 does not suffer from output voltage phase reversal

that occurs in some op amps when the specified input VCM range is

exceeded. Output voltage phase reversal causes the output voltage

to swing to the opposite rail until the input comes back within

the common-mode range. Typically, the inputs of conventional op

amps fail to reach or exceed the common-mode limit toward the

negative range. Phase-reversal is most often associated with junc-

tion field effect transistor (JFET) and/or bipolar field effect transistor

(BiFET) amplifiers, but some bipolar single-supply amplifiers are

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