What is a Gap Capacitor?

Gap capacitors are a type of SMT capacitor used in high-frequency applications. They are essentially 2 single-layer capacitors placed in series with a ‘GAP’ between them (see figure below). This structure is integrated using a strip-line or co-planar waveguide design that does not require any bond wires, thereby reducing its size, minimizing the parasitic inductance / resistance and providing a low insertion loss.

Source: Knowles Capacitors - Structure and Equivalent Capacitance of a Gap Capacitor

Gap Capacitors can achieve up to 20 times more capacitance than other SMT capacitors because of their unique internal electrode layout, which provides more capacitance from the same dielectric material. They are usually available with capacitance values from 0.01pF to 24000pF (based on what we could find from the companies who make them – Click here to see GAP capacitors from the leading manufacturers). 

Gap Capacitors are optimized for high-frequency applications through a combination of material selection, advanced construction techniques, high Q factor, thermal stability, and careful design to minimize parasitic effects. These optimizations ensure that the capacitors can efficiently handle high-frequency signals with minimal losses. 

Gap Capacitor Materials 

Gap Capacitors are made of materials with low dielectric losses like ceramics (e.g., porcelain, mica) or certain plastics (e.g., PTFE, polyethylene) are used to minimize energy dissipation. They also use high permittivity materials (like mica, muscovite, alumina, etc) to achieve higher capacitance values without increasing the physical size.

Advantages of Gap Capacitor: 

• High Frequency Operation (Usually up to 30 GHz, can be higher as well)
• Does not require wire bonding because it can be surface-mounted, or flip-chip mounted.
• Higher Capacitance Values over other capacitor types using the same dielectric material
• Low Inductive and Resistive parasitics 
• Low Insertion Loss, with less than 5 dB loss at 1 GHz and less than 1 dB loss at 67 GHz and low manufacturing loss due to efficient design  

Applications of Gap capacitors:

• Used in RF circuits for tuning, coupling, and filtering. 
• Commonly found in devices like transmitters, receivers, amplifiers, and oscillators. 
• Employed in impedance matching networks to ensure maximum power transfer between different stages of an RF circuit. 
• It is useful for DC blocking and RF Bypassing. 

Click here to see Gap Capacitors from the leading manufacturers.