**The AD835AR: A Comprehensive Analysis of the 250 MHz Voltage Output Analog Multiplier IC**

In the realm of analog computation and signal processing, the multiplier is a fundamental building block, enabling functions from modulation to power measurement. Among the various integrated circuits developed for this purpose, the **AD835AR from Analog Devices stands out as a high-performance, versatile solution**. This article provides a comprehensive analysis of this influential component, delving into its architecture, key features, and primary applications.

The AD835AR is a monolithic, **four-quadrant voltage output analog multiplier** designed for operation at frequencies up to 250 MHz. Its core function is to accurately produce an output voltage (`W`) that is the linear product of two differential input voltages (`X = X1 - X2` and `Y = Y1 - Y2`) divided by a reference voltage (`U`), following the transfer function: **W = (X * Y) / U + Z**. The `Z` input allows for the addition of an offset voltage, enhancing its flexibility in various circuit configurations.

A key to its high-speed performance is its **advanced voltage-mode architecture**. Unlike older current-mode multipliers (e.g., those based on the Gilbert cell), the AD835AR is fabricated on a proprietary complementary bipolar process. This design allows it to maintain a **remarkable -3 dB bandwidth of 250 MHz** with a very low harmonic distortion, typically -46 dBc at 10 MHz. This makes it exceptionally suitable for high-frequency applications where signal fidelity is paramount.

Beyond its sheer speed, the AD835AR is engineered for simplicity and ease of use. It features a **simplified connection scheme**, often requiring only a single DC supply from 4.5 V to 12 V, though dual supplies can also be used. The device is laser-trimmed during manufacturing to ensure **high accuracy with low multiplicative error** (typically ±0.5%) and low offset voltage. This precision eliminates the need for external trimming components in most applications, saving board space and design time.

The applications of the AD835AR are vast and varied, capitalizing on its ability to perform real-time analog multiplication. It is ideally suited for:

* **Modulation/Demodulation:** Serving as a high-frequency amplitude modulator (AM), double-sideband suppressed-carrier (DSB-SC) modulator, or phase-sensitive detector.

* **Squaring and Frequency Doubling:** When both inputs are driven by the same signal, the output is a perfect square of the input, effectively doubling its frequency.

* **True RMS-to-DC Conversion:** By squaring an input signal and integrating it, the IC can form the core of an accurate RMS measurement circuit.

* **Automatic Gain Control (AGC) and Voltage-Controlled Amplifiers (VCA):** Using one input for the signal and the other for a control voltage.

* **Analog Computing:** Implementing complex functions like division (with an op-amp in the feedback loop) and correlation.

**ICGOODFIND:** The AD835AR is a cornerstone component in high-speed analog design. Its combination of a **250 MHz bandwidth, voltage-output operation, and exceptional ease of use** solidifies its position as a go-to solution for engineers designing demanding RF and signal processing systems. It successfully bridges the gap between theoretical function and practical, high-performance implementation.

**Keywords:** Analog Multiplier, 250 MHz Bandwidth, Voltage Output, High-Speed Signal Processing, Four-Quadrant Multiplication.