The **AOM-4540P-R** is a high-sensitivity, omnidirectional electret condenser microphone (ECM) capsule. It is widely used in telecommunications, security systems, and consumer electronics due to its compact size and reliable performance. --- ### ## Technical Specifications The following table outlines the key electrical and physical characteristics of the AOM-4540P-R: | Parameter | Specification | | :--- | :--- | | **Type** | Electret Condenser (ECM) | | **Directivity** | Omnidirectional | | **Sensitivity** | -40 ± 3 dB (0dB = 1V/Pa @ 1kHz) | | **Operating Voltage** | 1.0V – 10V DC (Standard: 2.0V) | | **Current Consumption** | Max 0.5 mA | | **Frequency Range** | 20 Hz – 20,000 Hz | | **Signal-to-Noise Ratio** | > 60 dB | | **Impedance** | 2.2 kΩ (Max) | | **Dimensions** | 9.7mm (Diameter) x 4.5mm (Height) | | **Connection Type** | Through-hole (Solder Pins) | --- ### ## Internal Structure and Components The device consists of several critical electronic and mechanical parts: 1. **Electret Diaphragm:** A thin plastic film with a permanent electrostatic charge. When sound waves hit this film, it vibrates, changing the capacitance. 2. **Back Plate:** A stationary metal plate that acts as the other half of the capacitor. 3. **JFET (Field Effect Transistor):** Because the impedance of the capsule is extremely high, a built-in JFET acts as an **impedance converter**. It converts the high-impedance signal into a lower-impedance signal usable by standard audio pre-amplifiers. 4. **Casing:** A cylindrical aluminum housing that provides electromagnetic shielding to reduce hum and interference. --- ### ## Typical Application Circuit To function correctly, the AOM-4540P-R requires a DC bias voltage. A common configuration is the "Common Source" amplifier circuit: ```text [VCC (2.0V)] | [RL (2.2k Ohm Resistor)] | +---- [Output Capacitor (0.1uF - 10uF)] ----> To Pre-Amp | [AOM-4540P-R Pin (+)] [AOM-4540P-R Pin (-)] | [GND] ``` --- ### ## Key Features * **RoHS Compliant:** The "-R" suffix indicates compliance with environmental regulations regarding hazardous substances. * **Omnidirectional:** It picks up sound equally from all directions, making it ideal for ambient recording or conference devices. * **Broad Frequency Response:** Capable of capturing high-fidelity audio across the human hearing range.