MAX4230-MAX4234 データシートの表示（PDF） - Maxim Integrated

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MAX4230-MAX4234

High-Output-Drive, 10MHz, 10V/µs, Rail-to-Rail I/O Op Amps with Shutdown in SC70

Maxim Integrated 

High-Output-Drive, 10MHz, 10V/µs,

Rail-to-Rail I/O Op Amps with Shutdown in SC70

0.5VP-P

C1 R1

0.1μF 16kΩ

3V

R5

51kΩ

C2

0.1μF

R6

51kΩ

R2

82kΩ

3V

28

1/2

MAX4232

1

3

4

R3

10kΩ

R4

10kΩ

32Ω

fs = 100Hz

6

7

5

1/2

MAX4232

Figure 3. Dual MAX4230/MAX4231 Bridge Amplifier for 200mW

at 3V

Choose gain-setting resistors RIN and RF according to

the amount of desired gain, keeping in mind the maxi-

mum output amplitude. The output coupling capacitor,

COUT, blocks the DC component of the amplifier out-

put, preventing DC current flowing to the load. The out-

put capacitor and the load impedance form a highpass

filer with the -3dB point determined by:

f

−3dB

=

1

2πRLCOUT

For a 32Ω load, a 100µF aluminum electrolytic capaci-

tor gives a low-frequency pole at 50Hz.

Bridge Amplifier

The circuit shown in Figure 3 uses a dual MAX4230 to

implement a 3V, 200mW amplifier suitable for use in

size-constrained applications. This configuration elimi-

nates the need for the large coupling capacitor

required by the single op-amp speaker driver when sin-

gle-supply operation is necessary. Voltage gain is set

to 10V/V; however, it can be changed by adjusting the

82kΩ resistor value.

Rail-to-Rail Input Stage

The MAX4230–MAX4234 CMOS op amps have parallel-

connected n- and p-channel differential input stages

that combine to accept a common-mode range extend-

ing to both supply rails. The n-channel stage is active

for common-mode input voltages typically greater than

(VSS + 1.2V), and the p-channel stage is active for

common-mode input voltages typically less than (VDD -

1.2V).

VCC = 3.0V

RL = 100kΩ

IN

1V/div

OUT

1V/div

5μs/div

Figure 4. Rail-to-Rail Input/Output Range

Rail-to-Rail Output Stage

The minimum output is within millivolts of ground for sin-

gle-supply operation, where the load is referenced to

ground (VSS). Figure 4 shows the input voltage range

and the output voltage swing of a MAX4230 connected

as a voltage follower. The maximum output voltage

swing is load dependent; however, it is guaranteed to

be within 500mV of the positive rail (VDD = 2.7V) even

with maximum load (32Ω to ground).

Observe the Absolute Maximum Ratings for power dis-

sipation and output short-circuit duration (10s, max)

because the output current can exceed 200mA (see

the Typical Operating Characteristics.)

Input Capacitance

One consequence of the parallel-connected differential

input stages for rail-to-rail operation is a relatively large

input capacitance CIN (5pF typ). This introduces a pole

at frequency (2πR′CIN)-1, where R′ is the parallel combi-

nation of the gain-setting resistors for the inverting or

noninverting amplifier configuration (Figure 5). If the pole

frequency is less than or comparable to the unity-gain

bandwidth (10MHz), the phase margin is reduced, and

the amplifier exhibits degraded AC performance through

either ringing in the step response or sustained oscilla-

tions. The pole frequency is 10MHz when R′ = 2kΩ. To

maximize stability, R′ << 2kΩ is recommended.

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