The C1124 (commonly listed as 2SC1124) is a high-voltage NPN silicon transistor primarily designed for applications requiring high-voltage switching and amplification, such as video output stages in television receivers or high-voltage power supplies. 1. Technical Specifications
According to data found on AllTransistors, the key electrical characteristics are as follows: Material Silicon (Si) Polarity Collector-Base Voltage VCBOcap V sub cap C cap B cap O end-sub Collector-Emitter Voltage VCEOcap V sub cap C cap E cap O end-sub Emitter-Base Voltage VEBOcap V sub cap E cap B cap O end-sub Max Collector Current ICcap I sub cap C Total Power Dissipation PCcap P sub cap C Transition Frequency fTf sub cap T DC Current Gain hFEh sub cap F cap E end-sub Operating Temperature Tjcap T sub j 2. Physical & Packaging Details
Package Type: Typically found in the TO-202 or similar power packages designed for heat sink mounting.
Pin Configuration: Viewed from the front (flat side with markings): Emitter
Collector (often connected to the metal tab for heat dissipation) Base 3. Key Applications Video Output: High-frequency response ( ) and high voltage ( ) make it suitable for driving CRT cathodes.
Voltage Regulators: Used in high-voltage DC-DC converters or linear regulators.
Industrial Switching: General-purpose switching where voltage exceeds standard low-power transistor limits ( 4. Cross-Reference & Equivalents
If you cannot find the original 2SC1124, technical resources like AllDatasheet and AllTransistors suggest considering these alternatives, though you should always verify pinouts and power ratings:
2SC1122: Similar characteristics but may have different gain brackets.
MJE340: A modern, widely available high-voltage NPN transistor (often in TO-126) used for similar video/high-voltage tasks. BF459: Another common video output transistor.
Caution: Always ensure a proper heat sink is used if the transistor is operating near its
power limit to prevent thermal runaway or failure at the maximum junction temperature.
1. Alldatasheet.com (Enhanced Version)
Use the "View Original" or "Translated" option. Look for the datasheet uploaded by Hitachi from 1983 – it has the clearest SOA graph.
The "Better" Datasheet Specs (The Important Stuff)
Most datasheets give you raw numbers. Here is what they actually mean:
| Parameter | Value | The Real-World Meaning | | :--- | :--- | :--- | | Collector-Base Voltage (VCBO) | 60V | Don't put more than 60V between C and B. Safe for 48V rails. | | Collector-Emitter Voltage (VCEO) | 30V | Critical: This is lower than Vcbo. Do NOT run 60V here. | | Emitter-Base Voltage (VEBO) | 5V | Keep base drive low. | | Collector Current (IC) | 100mA | Low power. Not for drivers or outputs >1W. | | Power Dissipation (Pc) | 2.5W | Use a small heatsink above 1W continuous. | | Gain (hFE) | 40 – 240 | Highly variable by batch. Design for the low end (40). | | Transition Frequency (fT) | 250 MHz (min) | Why it's special: Works well up to ~150 MHz. |
1. Safe Operating Area (SOA)
The original C1124 datasheet lacked a detailed SOA graph. A modern "better" datasheet (like for the TIP41C) shows exactly how much current you can draw at specific voltages. Better datasheets save your circuit from blowing up.
Mastering the C1124 Transistor: Datasheet Deep Dive & Superior Alternatives
If you are working on vintage audio equipment, old CRT monitors, or industrial control boards, you have likely come across the 2SC1124 transistor. While this component was a workhorse in its prime, obtaining a clear datasheet or finding a reliable replacement can be challenging today.
This guide breaks down the critical specifications of the C1124, explains how to read the datasheet effectively, and suggests "better" modern alternatives for your repair projects.
8. Quick Verification Before Use
- Check continuity between C and E – should be open (both directions).
- Diode B→E forward drop ~0.6V, reverse infinite.
- Diode B→C similarly ~0.6V.
- If any short or low resistance (<100Ω) between any pins, it's dead or counterfeit.