This article introduces the use of the amplifier’s multi-channel amplifier channel isolation parameters and absolute maximum ratings. This concludes the discussion on the use of general amplifier parameters.

This article introduces the use of the amplifier’s multi-channel amplifier channel isolation parameters and absolute maximum ratings. This concludes the discussion on the use of general amplifier parameters.

1. Multi-channel amplifier channel isolation

The amplifier channel isolation (MULTIPLE AMPLIFIERS CHANNEL SEPARATION, Cs) is used to evaluate the degree of interference between channels. It is defined as the degree of isolation between the output voltage change of the driven channel and other channels in a multi-channel amplifier. The unit is decibel.

As shown in Figure 2.6, ADA4077-2 and ADA4077-4 are powered at ±15V, and the multi-channel amplifier channel isolation is -125dB at 1KHz. It means that if the peak-to-peak output signal of one channel is 1V and the frequency is 1KHz, other channels will produce a peak-to-peak signal of the same frequency with 562.3nV.

Brief analysis: the use of multi-channel amplifier channel isolation parameters and absolute maximum ratings
Figure 2.6 ADA4077 multi-channel isolation and noise parameters

The channel isolation of the multi-channel amplifier will become worse as the frequency increases. As shown in figure 2.184, the channel isolation of ADA4077-2 and ADA4077-4 is -78dB at 100KHz and -69dB at 1MHz. Therefore, in the high-frequency signal conditioning circuit, it is necessary to pay attention to the use of single-channel amplifiers first.

Brief analysis: the use of multi-channel amplifier channel isolation parameters and absolute maximum ratings
Figure 2.184 The relationship between ADA4077 channel isolation and frequency

2.Absolute maximum ratings

Absolute maximum ratings (ABSOLUTE MAXIMUM RATINGS) are the maximum ratings that the chip can withstand. It does not mean that the device can work normally under these conditions. Long-term operation in conditions beyond the maximum rating may cause permanent damage to the chip. Such damage will occur with a certain probability during long-term operation.

The author has encountered a case of exceeding the absolute maximum rating design once in the industry. As shown in Figure 2.187, the absolute maximum rating of an analog switch ADG1408. Among them, the voltage from the positive power rail to the negative power rail of the power supply is 35V, but the maximum voltage from the positive and negative power rails to the ground is 25V. The engineer designed the positive power supply to be +30V and the negative power supply to -3V. In order to achieve the maximum input signal value of 28V, the chip burned out occasionally in the small batch test of the product, and it was necessary to reserve replacement motherboards in proportion. Therefore, during project rectification, it is recommended to replace with a wide-voltage analog switch to ensure long-term reliable operation of the product.

Brief analysis: the use of multi-channel amplifier channel isolation parameters and absolute maximum ratings
Figure 2.187 ADG1408 Absolute Maximum Ratings

Figure 2.188 shows the absolute maximum ratings of ADA4077, including the operating voltage (Supply Voltage, Vsy) is 36V, the input voltage (Input Voltage) is ±Vsy, the input current (Input Current) is ±10mA, and the differential input range (Differential Input Voltage) )±Vsy, Output Short-Circuit Duration to GND is undefined, Storage Temperature Range is -65℃ to +150℃, Operating Temperature Range is -45 ℃ to +120℃, Junction Temperature Range (Junction Temperature Range) is -65℃ to +150℃, Lead Temperature, Soldering, 10 seconds soldering is 300℃. Maximum Reflow Temperature (Maximum Reflow Temperature) 260℃, Human Body Model (HBM) Electrostatic Discharge (ESD) is 6KV, Field Induced Charge Device Model (Field Induced Charge Device Model, FICDM) Electrostatic Discharge (Electrostatic Discharge) , ESD) is 1.25KV.

Brief analysis: the use of multi-channel amplifier channel isolation parameters and absolute maximum ratings
Figure 2.188 ADA4077 Absolute Maximum Ratings

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