Data Sheet

MAX74810

analog.com

Rev. 0

20 of 23

APPLICATIONS INFORMATION

Use of Large Source Resistance

The MAX74810 is designed to work with low value source resistance. Note that the amplifier has an ultralow voltage

noise density of 5.8nV/√Hz. A 1kΩ resistor contributes 4nV/√Hz; therefore, placing a 1kΩ resistor at the input

increases total noise to 7nV/√Hz. For this reason (noise), it is recommended to avoid using large source resistance.

Unity Gain Follower with Large Source Resistance

When the MAX74810 is configured in a unity-gain follower configuration with a large source resistance and slow

power supply ramp rate, the amplifier output may rail to the positive supply.

Figure 53. Insert RF When Large RS is Used

Workaround

To avoid the amplifier output railing to the positive supply, implement one of the following actions (see Table 6 and

Figure 53):



Reduce the value of the source resistance (RS).



Insert a feedback resistor (RF).

Table 6. Amplifier Output Railing Workaround Recommendations

CONDITION

RECOMMENDATION

1.5V ≤ VSY − VIN < 2.5V

RF = 200Ω or RF ≥ 50RS, whichever is greater

2.5V ≤ VSY − VIN < 3.5V

RS ≤ 200Ω or RF ≥ 2RS

VSY − VIN ≥ 3.5V

RS ≤ 500Ω or RF ≥ 0.5RS

MAX74810

+VSY

RF

RS

VOUT

–VSY

VIN