MAX4309 查看數據表（PDF） - Maxim Integrated

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MAX4309

400MHz, Ultra-Low-Distortion Op Amps

Maxim Integrated 

400MHz, Ultra-Low-Distortion Op Amps

_____________________Pin Description

PIN NAME

FUNCTION

1

N.C. No Connection. Not internally connected.

2

IN- Inverting Input

3

IN+ Noninverting Input

4, 5

VEE Negative Power Supply, connect to -5VDC.

6

OUT Amplifier Output

7, 8

VCC Positive Power Supply, connect to +5VDC.

_______________Detailed Description

Choosing Resistor Values

Unity-Gain Configuration

The MAX4108 is internally compensated for unity gain.

When configured for unity gain, the device requires a

small resistor in series with the feedback path. This

resistor improves the AC response by reducing the Q

of the tank circuit, which is formed by parasitic feed-

back inductance and capacitance.

Inverting and Noninverting Configurations

The values of the gain-setting feedback and input resis-

tors are important design considerations. Large resistor

values will increase voltage noise, and will interact with

the amplifier’s input and PC board capacitance to gen-

erate undesirable poles and zeros, which can decrease

bandwidth or cause oscillations. For example, a nonin-

verting gain of +2, using 1kΩ resistors combined with

2pF of input capacitance and 0.5pF of board capaci-

tance, will cause a feedback pole at 128MHz. If this

pole is within the anticipated amplifier bandwidth, it will

jeopardize stability. Reducing these 1kΩ resistors to

100Ω will extend the pole frequency to 1.28GHz, but

could limit output swing by adding 200Ω in parallel with

the amplifier’s load. Clearly, the selection of resistor val-

ues must be tailored to the specific application.

The MAX4108/MAX4109/MAX4308/MAX4309 are ultra-

low-distortion, high-bandwidth op amps. The output

distortion will be degraded as the total load resistance

seen by the amplifier decreases. To minimize distortion

products, keep the input and gain-setting resistors rela-

tively large. A 500Ω feedback resistor combined with

an appropriate input resistor to set the gain will provide

excellent AC performance without significantly increas-

ing distortion.

RG

RF

RS

VIN

CL

RL

PART

MAX4108

MAX4109

MAX4308

MAX4309

RF (Ω)

24

500

500

500

RG (Ω)

∞

500

125

56

GAIN (V/V)

1

2

5

10

Figure 1a. Using an Isolation Resistor for High Capacitive

Loads

25

MAX4108

20

MAX4308

15

MAX4109/MAX4309

10

5

0

10 40 70 100 130 160 190 220

CAPACITANCE (pF)

Figure 1b. Optimal Isolation Resistor (RS) vs. Capacitive Load

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