Hybrid vs. Monolithic Microwave IC (MMIC): Key Differences, Biasing and Manufacturers

Integrated Circuits (ICs) used in microwave engineering are broadly classified into Hybrid Integrated Circuits (Hybrid ICs) and Monolithic Microwave Integrated Circuits (MMICs). Both technologies integrate microwave components into compact assemblies, but they differ significantly in construction, manufacturing process, performance, cost and applications.

Hybrid ICs are assembled by mounting individual active and passive components on a common substrate, whereas MMICs integrate all active and passive elements onto a single semiconductor chip. Today, MMIC technology is widely used in satellite communication, radar, 5G systems, aerospace, defense, and wireless communication because of its compact size and excellent high frequency performance.

This page provides an overview of MMICs (Monolithic Microwave Integrated Circuits), including their biasing techniques and a list of manufacturers and suppliers.

What is Hybrid Integrated Circuit (Hybrid IC)

A Hybrid Integrated Circuit (Hybrid IC) is an electronic circuit in which separate semiconductor devices (transistors, diodes, etc.) and passive components (resistors, capacitors, inductors) are fabricated individually and then assembled on a common insulating substrate.

Unlike monolithic ICs, the components are not fabricated on a single semiconductor wafer.

Construction of Hybrid IC

A Hybrid IC typically consists of following:

• Ceramic or alumina substrate
• Thin film or thick film conductors
• Individually mounted semiconductor chips
• Chip resistors and capacitors
• Bonding wires
• Metal package with protective cover

The components are interconnected using wire bonding or conductive tracks printed on the substrate.

What is Monolithic Microwave Integrated Circuit (MMIC)

A Monolithic Microwave Integrated Circuit (MMIC) is a microwave integrated circuit in which all active and passive components are fabricated on a single semiconductor substrate using photolithographic semiconductor manufacturing processes.

The substrate is commonly made of following:

• Gallium Arsenide (GaAs)
• Gallium Nitride (GaN)
• Indium Phosphide (InP)
• Silicon Germanium (SiGe)
• CMOS silicon (for some RF applications)

An MMIC contains microwave transistors, diodes, resistors, capacitors, inductors, transmission lines and matching networks. All components are integrated onto a single semiconductor chip.

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.

Comparison Between Hybrid IC and Monolithic IC (MMIC)

Feature	Hybrid IC	Monolithic IC (MMIC)
Construction	Individual components mounted on a common substrate	All components fabricated on a single semiconductor chip
Manufacturing Method	Assembly of separately fabricated components	Photolithographic fabrication on one wafer
Integration Level	Moderate	Very high
Physical Size	Larger	Very compact
Operating Frequency	Suitable for microwave frequencies	Excellent performance at microwave and millimeter-wave frequencies
Parasitic Effects	Higher	Very low
Reliability	High	Very high
Repairability	Individual components may be replaced during manufacturing	Generally not repairable; entire chip is replaced
Design Flexibility	Easier to customize	Less flexible after fabrication
Production Cost	Lower for low-volume custom designs	Lower per unit in high-volume production but high initial development cost
Thermal Performance	Better heat dissipation due to discrete layout	Requires careful thermal design, especially for high-power devices
Typical Applications	Custom RF modules, military equipment, industrial microwave systems	5G, radar, satellite communication, aerospace, wireless devices

Popular MMIC Manufacturers/Suppliers

Here are a couple of well known manufacturers and suppliers with popular part numbers.

1. Mini-Circuits: Offers general purpose wideband MMIC amplifiers. You can search for specific MMIC devices based on your requirements on their website. Popular parts are PMA2-43LN+, GVA-84+, TSS-53+, PSA4-5043+.
2. Hittite (Now Analog Devices): Provides GaAs MMICs for various applications, including gain blocks, low noise amplification, linear power amplification, and wideband applications. Popular part numbers are HMC476MP86, HMC547ALC3, HMC8410, HMC463LP5.
3. Qorvo : TGA2595 (GaN Power Amplifier), TGA4046 (LNA), TQP3M9037 and QPA2211 (RF front end modules)
4. Renesas Electronics : F0440NBGI, F0392NBGI , functions as RF switches and synthesizer related MMICs
5. Skyworks Solutions : SKY67159-396LF, SKY65383-11, SKY67153-396LF, RF front end modules and LNAs

Summary

Hybrid ICs and Monolithic Microwave Integrated Circuits (MMICs) are both essential technologies in microwave engineering. Hybrid ICs provide flexibility, good thermal performance, and are suitable for specialized, lower volume applications. MMICs, on the other hand, offer very high integration, compact size, excellent microwave performance, and high reliability, making them the preferred choice for modern wireless communication, radar, aerospace, satellite, and 5G systems. The choice between the two depends on performance requirements, production volume, cost considerations and design flexibility.