Datasheet MAX4014, MAX4017, MAX4019, MAX4022 (Maxim) - 8

Low-Cost, High-Speed, Single-Supply, Gain of +2 Buffers with Rail-to-Rail Outputs in SOT23 _______________Detailed Description
+2V/V, ground the inverting terminal. Use the noninvert- ing terminal as the signal input of the buffer (Figure 1a). The MAX4014/MAX4017/MAX4019/MAX4022 are sin- Grounding the noninverting terminal and using the gle-supply, rail-to-rail output, voltage-feedback, closed- inverting terminal as the signal input configures the loop buffers that employ current-feedback techniques buffer for a gain of -1V/V (Figure 1b). to achieve 600V/µs slew rates and 200MHz band- widths. These buffers use internal 500Ω resistors to Since the inverting input exhibits a 500Ω input imped- provide a preset closed-loop gain of +2V/V in the non- ance, terminate the input with a 56Ω resistor when the inverting configuration or -1V/V in the inverting configu- device is configured for an inverting gain in 50Ω appli- ration. Excellent harmonic distortion and differential cations (terminate with 88Ω in 75Ω applications). gain/phase performance make these buffers an ideal Terminate the input with a 49.9Ω resistor in the nonin- choice for a wide variety of video and RF signal-pro- verting case. Output terminating resistors should direct- cessing applications. ly match cable impedances in either configuration. Local feedback around the buffer’ s output stage
Layout Techniques
ensures low output impedance, which reduces gain Maxim recommends using microstrip and stripline tech- sensitivity to load variations. This feedback also pro- niques to obtain full bandwidth. To ensure that the PC duces demand-driven current bias to the output tran- board does not degrade the buffer’s performance, design sistors for ±120mA drive capability, while constraining it for a frequency greater than 1GHz. Pay careful attention total supply current to less than 7mA. to inputs and outputs to avoid large parasitic capaci-
__________Applications Information
tance. Whether or not you use a constant-impedance board, observe the following guidelines when designing
Power Supplies
the board: These devices operate from a single +3.15V to +11V • Don’t use wire-wrapped boards. They are too inductive. power supply or from dual supplies of ±1.575V to • Don’t use IC sockets. They increase parasitic capac- ±5.5V. For single-supply operation, bypass the VCC pin itance and inductance. to ground with a 0.1µF capacitor as close to the pin as possible. If operating with dual supplies, bypass each • Use surface-mount instead of through-hole compon- supply with a 0.1µF capacitor. ents for better high-frequency performance. • Use a PC board with at least two layers; it should be
Selecting Gain Configuration
as free from voids as possible. Each buffer in the MAX4014 family can be configured for a voltage gain of +2V/V or -1V/V. For a gain of • Keep signal lines as short and as straight as possi- ble. Do not make 90° turns; round all corners.
MAX4014/MAX4017/MAX4019/MAX4022
IN+ IN+ IN *R *R OUT R OUT TIN OUT RS OUT *R *R 500Ω IN 500Ω IN- 500Ω 500Ω RTIN MAX40_ _ IN- MAX40_ _ *RL = 2R *RL = 2R Figure 1a. Noninverting Gain Configuration (AV = +2V/V) Figure 1b. Inverting Gain Configuration (AV = -1V/V)
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