Q1. What is the ADA4622-4 / ADA4622-2 / ADA4622-1?
A1. The ADA4622-4 / ADA4622-2 / ADA4622-1 is the next generation of the AD824 / AD822 / AD820. It is a single supply, 30 V, 8 MHz, Low Bias Current, Single-Supply, RRO, Precision JFET Op Amp.
Q2. What are the benefits of using the ADA4622-4 / ADA4622-2 / ADA4622-1 compared to the AD824 / AD822 / AD820?
A2. The ADA4622-4 / ADA4622-2 / ADA4622-1 includes many improvements that make it desirable as an upgrade without compromising the flexibility and ease of use that makes the AD824 / AD822 / AD820 useful for a wide variety of uses and applications. The input voltage range includes the negative supply and the output swings rail-to-rail. Input EMI filters are added to increase the signal robustness in the face of closely located switching noise sources. The speed in terms of bandwidth and slew rate is increased along with a strong output drive to improve settling time performance and enable the device to drive the inputs of modern single-ended successive approximation register analog to-digital converters (SAR ADCs).Voltage noise is reduced, both broadband by 25% and 1/f by half, while holding the supply current constant. DC precision is improved over the AD824 / AD822 / AD820 with half the offset and a maximum thermal drift specification is added to the ADA4622-4 / ADA4622-2 / ADA4622-1. The common-mode rejection ratio is improved over the AD824 / AD822 / AD820 to make the ADA4622-4 / ADA4622-2 / ADA4622-1 more suitable than the AD824 / AD822 / AD820 when used in non-inverting gain and difference amplifier configurations.
Q3. What parts and packages are available in the ADA4622 family?
A3. The ADA4622-4 is available in SOIC and LFCSP. The ADA4622-2 is available in an SOIC, MSOP and LFCSP package. The ADA4622-1 is available in SOIC and SOT23.
Q4. What about product grades? Is there an A and B grade ?
A4. Yes. Similar to other amplifiers the ADA4622-2 / ADA4622-1 B-grade has the best performance offset voltage and offset voltage drift vs. temperature (temp. co.) specifications. The ADA4622-4 is only available in A-grade. The ADA4622-2 / ADA4622-1 B-grade is only available in SOIC. The ADA4622-2 A-grade is available in both SOIC and MSOP. The ADA4622-1 A-grade is available in SOT23. The ADA4622-4 A grade is available in SOIC or LFCSP.
Q5. What applications is this part aimed at?
A5. The ADA4622-4 / ADA4622-2 / ADA4622-1 can be used in many different applications but it’s very low bias current mean it is particularly suited to interfacing with high output impedance sensor interfaces or photodiode sensor interfaces or any application which requires a transimpedance amplifier. The low bias current also means that the part is suitable for use in precision filters and signal conditioning and the strong drive strength and the ability to drive a 500 pF load directly means that the ADA4622-4 / ADA4622-2 / ADA4622-1 is also suitable for use as an ADC driver.
Q6. What tools are available to help me design-in the ADA4622-4 / ADA4622-2 / ADA4622-1?
A6. The ADA4622-4 / ADA4622-2 / ADA4622-1 are available in both the photodiode wizard tool and the filter wizard tool available on www.analog.com.
Q7. What about a SPICE model?
A7. The ADA4622 SPICE macro model is available to download from the each of the product page. The macro model contains no transistor models and so is very quick to simulate whilst providing and accurate model for simulation of typical parameters and circuit performance.
Q8. What precautions do I have to take to maintain the precision performance of the amplifier?
A8. Properly bypass the power supplies and keep the supply traces short to minimize power supply disturbances. Connect bypass capacitors as close as possible to the device supply pins. Keep the printed circuit board clean and free of moisture.
Q9. How will the external circuitry affect the total noise performance?
A9. The ADA4622-4 / ADA4622-2 / ADA4622-1 is designed for 12 nV/√Hz wideband input voltage noise and maintains low noise performance at low frequencies (see Figure 75 in the data sheet). This noise performance, along with the low input current as well as low current noise, means that the ADA4622-4 / ADA4622-2 / ADA4622-1 contributes negligible noise for applications with a source resistance greater than 10 kΩ and at signal bandwidths greater than 1 kHz.
Q10. What about phase reversal?
A10. The ADA4622-4 / ADA4622-2 / ADA4622-1 does not exhibit phase reversal for input voltages up to V+. For input voltages greater than V+, a 10 kΩ resistor in series with the non-inverting input prevents phase reversal at the expense of higher noise
Q11. Does ADA4622-1 include a shutdown function ?
A10. Yes. The ADA4622-1 in SOIC package includes a input pin which puts the amplifier into shutdown. In shutdown mode the part consumes approximately 50µA of current. The input voltage levels are reference to V-. If the input is connected to V- the part will enter shutdown mode. Once the pin is brought 1.4 V above V- the part will exit shutdown mode. The pin should not be brought more than 5 V above V- to prevent damage to the input. The pin can be left floating and the part will operate as normal allowing for the part to be used as drop-in replacement for products where this pin is unconnected.
For more information please refer to the product data sheet available on www.analog.com