### Overview of ADA4938-1ACPZ-R2 The **ADA4938-1ACPZ-R2** is a high-performance, ultra-low distortion, differential amplifier manufactured by **Analog Devices**. It is specifically designed to drive high-resolution, high-speed Analog-to-Digital Converters (ADCs) with performance reaching up to 16 bits. --- ### Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Type** | Fully Differential Amplifier | | **Number of Channels** | 1 (Single) | | **-3 dB Bandwidth** | 1.0 GHz (at G=1) | | **Slew Rate** | 4700 V/µs | | **Input Voltage Noise** | 2.6 nV/√Hz | | **Harmonic Distortion** | -104 dBc HD2 / -95 dBc HD3 (at 10 MHz) | | **Operating Supply Voltage** | 3.3 V to 5 V | | **Package** | 16-LFCSP (3mm x 3mm) | --- ### Core Electronic Characteristics #### 1. Differential Architecture Unlike standard operational amplifiers, the ADA4938-1 has differential inputs and differential outputs. This allows it to: * Convert single-ended signals to differential signals. * Minimize common-mode noise and electromagnetic interference (EMI). * Maximize the dynamic range of the signal chain. #### 2. VOCM Pin (Output Common-Mode Control) A critical feature of this part is the **VOCM pin**. By applying a voltage to this pin, the user can independently set the output common-mode level. This is vital when interfacing with high-speed ADCs that require a specific input offset voltage to function correctly. #### 3. Low Noise and Distortion The device is optimized for "SFDR" (Spurious-Free Dynamic Range). At high frequencies, it maintains extremely low harmonic distortion, which prevents the amplifier from introducing artifacts into the digital representation of the signal. --- ### Internal Functional Diagram Concept The internal circuitry consists of a high-speed core with internal feedback resistors that can be supplemented with external resistors to set the gain: ```text Input (+) ----[ Rf ]---- Output (-) | | ( - )--( + ) <-- High Speed Internal Op-Amp | | Input (-) ----[ Rf ]---- Output (+) | [VOCM] (Common Mode Control) ``` --- ### Typical Applications * **ADC Driving:** Primarily used to buffer and drive 14-bit to 16-bit ADCs (like the AD9467). * **Signal Level Shifting:** Adjusting signals to match the input requirements of downstream processors. * **Communications:** Used in base stations and radio receivers for IF (Intermediate Frequency) sampling. * **Instrumentation:** High-speed data acquisition systems and pulse amplifiers.