MJL21195

The MJL21195 is a PNP silicon power transistor from ON Semiconductor, part of a complementary pair with the NPN MJL21196. These devices utilize Perforated Emitter technology – an advanced manufacturing technique that creates an emitter structure with numerous small emitter segments, improving current distribution, reducing thermal resistance, and enhancing gain linearity across the operating current range. The result is a power transistor with exceptionally low harmonic distortion, making it highly sought after for high-fidelity audio amplifier designs. With a collector-emitter voltage rating of 250V (and 400V collector-base voltage), 16A continuous collector current capability, and 200W total power dissipation, these devices can handle substantial output power in push-pull amplifier configurations. The ‘MJL’ prefix indicates the Motorola-Japanese lineage (originally Motorola Semiconductor, later ON Semiconductor). The MJL21195/21196 pair has become a favorite among audio designers and audiophiles for their smooth, musical sound characteristics and robust build quality. The high safe operating area (SOA) of 2.5A at 80V for 1 second ensures reliable operation under demanding transient conditions. The TO-264 (also known as TO-3P) through-hole package provides excellent thermal conduction to the heatsink, with a thermal resistance of only 0.7°C/W from junction to case. The device is fully Pb-free and RoHS compliant, meeting current environmental standards.

The MJL21195 is a PNP bipolar junction transistor that operates as a current-controlled current amplifier. In a PNP device, the emitter is doped with holes (positive charge carriers), and current flows from the emitter to the collector when the base-emitter junction is forward-biased (base negative relative to emitter). The perforated emitter technology used in the MJL21195 significantly improves performance compared to conventional emitter structures. Instead of a single continuous emitter region, the perforated emitter design consists of many small emitter fingers or dots distributed across the active area. This provides several advantages: 1) More uniform current distribution across the die, reducing current crowding at the edges; 2) Lower emitter resistance due to the parallel connection of many small emitter segments; 3) Improved thermal distribution; 4) Better gain linearity across the full current range. For audio applications, the gain linearity is particularly important because nonlinear gain produces harmonic distortion. The MJL21195’s flat gain characteristic over a wide current range results in very low total harmonic distortion (THD). In typical push-pull audio amplifier configurations, the MJL21195 (PNP) handles the negative half of the audio waveform while its complementary NPN counterpart (MJL21196) handles the positive half. Proper biasing ensures both devices conduct slightly at the crossover point, minimizing crossover distortion. The high SOA rating means the transistor can withstand simultaneous high voltage and high current conditions that occur during transient signal peaks and reactive load conditions common with loudspeaker loads.

• High-end high-fidelity (Hi-Fi) audio power amplifiers
• Complementary push-pull audio output stages
• Linear power supply series-pass regulators
• Disk drive head positioners and precision servos
• Industrial linear power amplifiers and drivers
• Instrumentation and test equipment power stages