The **O2201** is a high-performance **Single-Chip Optically Isolated Error Amplifier**. It is primarily used in power supply designs to provide feedback across an isolation boundary while maintaining high precision and stability. --- ### 1. Key Internal Components The O2201 integrates three major functional blocks into a single package: | Component | Description | | :--- | :--- | | **Reference Voltage** | A high-precision 1.24V bandgap reference with low temperature drift. | | **Error Amplifier** | An operational amplifier that compares the feedback voltage to the internal reference. | | **Optocoupler** | An internal LED and phototransistor pair that transmits the error signal across the isolation barrier. | --- ### 2. Technical Specifications Below are the typical electrical characteristics for the O2201: | Parameter | Value (Typical) | | :--- | :--- | | **Reference Voltage ($V_{ref}$)** | 1.24V ($\pm 1\%$) | | **Isolation Voltage** | 5000 Vrms | | **Operating Current ($I_C$)** | 10 mA to 20 mA | | **Current Transfer Ratio (CTR)** | 100% to 200% | | **Bandwidth** | 200 kHz | --- ### 3. Pin Configuration The device is usually found in an 8-pin DIP or SOP package. 1. **COMP:** External compensation pin for the error amplifier. 2. **FB:** Feedback input (connected to the output voltage divider). 3. **GND:** Ground for the secondary side. 4. **NC:** No connection. 5. **Vcc:** Power supply for the primary side (collector of phototransistor). 6. **OUT:** Output signal (emitter of phototransistor). 7. **GND (Pri):** Ground for the primary side. 8. **LED:** Anode of the internal LED (often internally connected). --- ### 4. Application and Advantages The O2201 is designed to replace the common "TL431 + Optocoupler" combination used in Switching Mode Power Supplies (SMPS). * **Space Saving:** Consolidates two discrete components into one. * **Improved Frequency Response:** Eliminates the poles/zeros associated with the interaction between a discrete TL431 and a separate optocoupler. * **Accuracy:** Reduces the error budget by eliminating the tolerance mismatch between separate components. --- ### 5. Typical Circuit Usage ```c // Simplified Feedback Path [Output Voltage] -> [Resistor Divider] -> [FB Pin (O2201)] [FB Pin] vs [1.24V Internal Ref] -> [Error Amp] -> [Internal LED] [Internal Phototransistor] -> [PWM Controller Feedback Pin] ```