RHF310AK01V 데이터 시트보기 (PDF) - STMicroelectronics

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RHF310AK01V

Rad-hard 400 µA high-speed operational amplifier

STMicroelectronics 

RHF310A

Device description and operation

6

Device description and operation

6.1

6.1.1

Power supply considerations

Correct power supply bypassing is very important for optimizing the performance of the device in high-frequency

ranges. The bypass capacitors should be placed as close as possible to the IC pins to improve high-frequency

bypassing. A capacitor greater than 1 µF is necessary to minimize the distortion. For better quality bypassing, a

capacitor of 10 nF can be added, which should also be placed as close as possible to the IC pins. The bypass

capacitors must be incorporated for both the negative and positive supply.

Figure 23. Circuit for power supply bypassing

+VCC

10 µF

+

10 nF

+

-

10 nF

10 µF

+

-VCC

Single power supply

If you use a single-supply system, biasing is necessary to obtain a positive output dynamic range between the 0 V

and VCC supply rails. Considering the values of VOH and VOL, the amplifier provides an output swing from 0.9 V to

4.1 V on a 1 kΩ load.

The amplifier must be biased with a mid-supply (nominally VCC/2) in order to maintain the DC component of the

signal at this value. Several options are possible to provide this bias supply, such as a virtual ground using an

operational amplifier or a two-resistance divider (which is the cheapest solution). A high resistance value is

required to limit the current consumption. On the other hand, the current must be high enough to bias the non-

inverting input of the amplifier. If we consider this bias current (55 µA maximum) as 1 % of the current through the

resistance divider, two resistances of 470 Ω can be used to maintain a mid-supply.

The input provides a high-pass filter with a break frequency below 10 Hz, which is necessary to remove the

original 0 V DC component of the input signal and to set it at VCC/2.

Figure 25. Circuit for +5 V single supply illustrates a 5 V single power supply configuration.

A capacitor CG is added in the gain network to ensure a unity gain at low frequencies to keep the right DC

component at the output. CG contributes to a high-pass filter with Rfb//RG and its value is calculated with regard to

the cut-off frequency of this low-pass filter.

DS6201 - Rev 7

page 11/25

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