Understanding MMICs: Monolithic Microwave Integrated Circuits

This page provides an overview of MMICs (Monolithic Microwave Integrated Circuits), including their biasing techniques and a list of manufacturers and suppliers. Microwave ICs are created using either hybrid or monolithic techniques on various dielectric substrate materials.

Hybrid vs. Monolithic ICs

In a hybrid IC, circuit interconnections are made using metal lines deposited on an insulating substrate.

In a monolithic IC, all components are formed using processes like diffusion or ion implantation, altering the physical properties of the substrate material. Interconnections in a hybrid MIC are similar to those in thin-film hybrid ICs. In contrast, in a monolithic microwave IC, active devices are fabricated within a single semiconductor block and connected via metal lines or wires.

What is an MMIC?

MMIC stands for Monolithic Microwave Integrated Circuit. Different MMICs are designed for specific functions, such as mixing or amplification.

Various materials are used in MMIC construction, including:

• GaAs (Gallium Arsenide)
• InP (Indium Phosphide)
• GaN (Gallium Nitride)
• SiGe (Silicon Germanium)

Biasing an MMIC

Let’s examine a passive biasing configuration for a silicon bipolar MMIC amplifier. Beyond matching the MMIC to a 50 Ohm line, properly biasing the MMIC is crucial for optimal performance.

MMIC Bias Circuit

As illustrated, RF designers must consult the specific datasheet for the MMIC (e.g., MSA 1110 or ERA series from Minicircuits).

MMIC Bias Resistor Equation

The bias resistor value can be calculated using the following equation:

$Ib = \frac{V_{CC} - V_d}{R_b}$

Where:

• $I_b$ is the bias current.
• $V_{CC}$ is the supply voltage.
• $V_d$ is the device voltage.
• $R_b$ is the bias resistor.

Typically, $V_d$, $V_{CC}$, and $I_b$ are provided in the amplifier’s datasheet.

Popular MMIC Manufacturers/Suppliers

Here are a couple of well-known manufacturers and suppliers:

1. Mini-Circuits: Offers general-purpose wideband MMIC amplifiers. You can search for specific MMIC devices based on your requirements on their website.
2. Hittite (Now Analog Devices): Provides GaAs MMICs for various applications, including gain blocks, low-noise amplification, linear power amplification, and wideband applications.