Over the years, generally there are 3 types of circuitry: Analog, Analog Programmable, and Digital.

Analog hearing aids offer basic amplification with some adjustments of trimmers and/or volume control available. They are not as adjustable for future changes in hearing loss, and tend to not perform as well in background noise as programmable or fully digital hearing aids. The hearing aids are usually noisy and bulky. This is the first generation ofhearing aid technology.

Analog and Programmable aids are the predecessors to fully digital hearing aids. They were hot in the market in late 1980's and the 1990's. They could be programmed with memories, but the circuitry is still analog that is not adjustable per the hearing loss and hearing change. They typically have less advanced features than their fully digital counterparts, but did offer high sound quality and more adjustment options than conventional hearing aids. This is the second generation of hearing aid technology

Digital hearing aids came into play in the mid-1990's. Now, just like computers, digital cameras, and other digital devices, the digital technology exploded very fast. The digital aid can offer the most advanced sound processing and the greatest benefit to most people with a hearing loss. They are also usually the easiest aids for a new user to get accustomed to. Now, more than 95% of the hearing aids are digital.

They are highly adjustable – they can be reprogrammed using a computer if your hearing loss changes, or if only certain frequencies need to be modified. Some models come with very advanced features, such as feedback cancellation, directional microphones, and digital noise reduction.