Low Noise Microphone Preamplifier Circuit

The microphone preamplifier circuit design presented in this schematic utilizes the SSM2015 component manufactured by Precision Monolithics Inc. (PMI). This component provides high amplification with low noise characteristics (1.3nV/f). The design is configured to handle differential input signals and can achieve amplification levels ranging from 10 to 2000 times, depending on the value of resistor R4. When R5 is equal to R6, the amplification can be calculated using the formula A = (20000/R4) + 3.5.

The SSM2015 is a low-noise, high-gain instrumentation amplifier specifically designed for applications requiring precise amplification of small signals, such as those generated by microphones. The differential input capability allows the circuit to reject common-mode noise, enhancing the quality of the output signal.

In the schematic, the gain of the preamplifier is determined by the resistor R4, which is part of the feedback network. By varying R4, the user can set the desired gain within the specified range. The relationship between R4 and the overall gain is expressed in the formula A = (20000/R4) + 3.5, indicating that as the value of R4 increases, the gain decreases, and vice versa.

Resistors R5 and R6, when set equal, help to stabilize the gain and improve the linearity of the amplifier. The choice of these resistors should consider thermal noise and the overall impedance of the circuit to maintain optimal performance.

Additional components, such as capacitors for power supply decoupling and possibly additional filtering, may be included in the circuit design to ensure stable operation and minimize unwanted interference. Proper layout and grounding techniques are essential to prevent noise pickup and ensure that the low-level microphone signals are amplified accurately.

This microphone preamplifier circuit is suitable for various audio applications, including professional recording studios, public address systems, and any scenario where high-quality audio capture is essential.The microphone preamplifier circuit design presented in this schematic use SSM2015 produced by Precision Monolithics Inc. (PMI) which offers a high amplification and low noise ( 1. 3nV/ f). Has been designed to work with differential input signals and can deliver 10 to 2000x amplification and it is term of R4 value.

For R5 = R6 the amplification is A = (20000/R4)+3. 5 🔗 External reference