Datasheet MAX4230, MAX4231, MAX4232, MAX4233, MAX4234 (Maxim) - 10

link to page 10 link to page 10 link to page 2 link to page 5 link to page 11 MAX4230–MAX4234 High-Output-Drive, 10MHz, 10V/μs, Rail-to-Rail I/O Op Amps with Shutdown in SC70 C1 R1 R2 0.1mF V 16kΩ 82kΩ CC = 3.0V RL = 100kΩ 0.5VP-P 32W 3V 3V
1/2
fS = 100Hz IN 2 8
MAX4232
1V/div 1 R5 3 4 51kΩ R3 R4 10kΩ 10kΩ OUT C2 R6 6 1V/div 0.1µF 7 51kΩ 5
1/2 MAX4232
5µs/div Figure 3. Dual MAX4230/MAX4231 Bridge Amplifier for 200mW Figure 4. Rail-to-Rail Input/Output Range at 3V Choose gain-setting resistors RIN and RF according to
Rail-to-Rail Output Stage
the amount of desired gain, keeping in mind the maximum The minimum output is within millivolts of ground for output amplitude. The output coupling capacitor, COUT, single-supply operation, where the load is referenced to blocks the DC component of the amplifier output, prevent- ground (V ing DC current flowing to the load. The output capacitor SS). Figure 4 shows the input voltage range and the output voltage swing of a MAX4230 connected and the load impedance form a highpass filer with the as a voltage follower. The maximum output voltage swing -3dB point determined by: is load dependent; however, it is guaranteed to be within 1 500mV of the positive rail (VDD = 2.7V) even with maxi- f 3 − dB = mum load (32Ω to ground). 2 R π INCOUT Observe the Absolute Maximum Ratings for power dis- For a 32Ω load, a 100μF aluminum electrolytic capacitor sipation and output short-circuit duration (10s, max) gives a low-frequency pole at 50Hz. because the output current can exceed 200mA (see the Typical Operating Characteristics.)
Bridge Amplifier
The circuit shown in Figure 3 uses a dual MAX4230 to
Input Capacitance
implement a 3V, 200mW amplifier suitable for use in size- One consequence of the parallel-connected differential constrained applications. This configuration eliminates input stages for rail-to-rail operation is a relatively large the need for the large coupling capacitor required by the input capacitance CIN (5pF typ). This introduces a pole single op-amp speaker driver when single-supply opera- at frequency (2πR′CIN)-1, where R′ is the parallel com- tion is necessary. Voltage gain is set to 10V/V; however, bination of the gain-setting resistors for the inverting or it can be changed by adjusting the 82kΩ resistor value. noninverting amplifier configuration (Figure 5). If the pole frequency is less than or comparable to the unity-gain
Rail-to-Rail Input Stage
bandwidth (10MHz), the phase margin is reduced, and The MAX4230–MAX4234 CMOS op amps have parallel the amplifier exhibits degraded AC performance through connected n- and p-channel differential input stages that either ringing in the step response or sustained oscilla- combine to accept a common-mode range extending tions. The pole frequency is 10MHz when R′ = 2kΩ. To to both supply rails. The n-channel stage is active for maximize stability, R′ << 2kΩ is recommended. 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). www.maximintegrated.com Maxim Integrated │ 10