MPSA92 — -300V -500mA Ultra-High-Voltage PNP BJT (TO-92)

Overview

The MPSA92 (and KSP92 / MMBTA92) is an industry-standard ultra-high-voltage small-signal PNP bipolar junction transistor manufactured by onsemi, Fairchild, Central Semiconductor, and STMicroelectronics. Available in a through-hole TO-92 plastic package and surface-mount SOT-23 package with standard Emitter - Base - Collector (E-B-C) pinout, it is built specifically for extreme high-voltage switching and amplification.

Featuring a massive collector-emitter breakdown voltage ( $V_{CEO}$ ) rating of $-300\text{V}$ ( $-300\text{V}$ $V_{CBO}$ ), a continuous collector current rating of $-500\text{ mA}$ , and a transition frequency ( $f_T$ ) of $50\text{ MHz}$ , the MPSA92 is the undisputed complementary PNP pair to the iconic MPSA42. It is celebrated across the maker and retrocomputing community as the premier high-side anode switch for multiplexed $170\text{V} \dots 200\text{V}$ Nixie tube clocks, neon indicator arrays, gas discharge displays, CRT video drivers, and high-voltage constant current active loads.

Quick reference


Transistor Type	Ultra-High-Voltage Small-Signal Silicon PNP BJT
Package	TO-92 (3-pin through-hole) / SOT-23 (MMBTA92)
Collector-Emitter Breakdown ( $V_{CEO}$ )	$-300\text{ V}$ max
Collector-Base Breakdown ( $V_{CBO}$ )	$-300\text{ V}$ max
Emitter-Base Breakdown ( $V_{EBO}$ )	$-5.0\text{ V}$ max
Continuous Collector Current ( $I_C$ )	$-500\text{ mA}$ max
DC Current Gain ( $h_{FE}$ )	$40$ to $200$ ( $I_C = -10\text{mA}, V_{CE} = -10\text{V}$ ) / $\ge 25$ at $-30\text{mA}$
Transition Frequency ( $f_T$ )	$50\text{ MHz}$ min
Collector Saturation ( $V_{CE(sat)}$ )	$-0.50\text{ V}$ max at $I_C = -20\text{mA}, I_B = -2.0\text{mA}$
Total Power Dissipation ( $P_D$ )	$625\text{ mW}$ ( $T_A = 25^\circ\text{C}$ )
Complementary NPN Pair	MPSA42 / KSP42 (300V NPN BJT)

Pinout (TO-92 Package - E-B-C Standard)

Looking at the flat front face with leads pointing downward:

text

        ┌─────────┐
        │  TO-92  │
        │ MPSA92  │
        └─┬───┬───┬─┘
          1   2   3
          E   B   C

Pin	Name	Type	Description
1	`EMITTER (E)`	Emitter Terminal	Emitter (Connect to $+170\text{V} \dots +200\text{V}$ high-voltage anode supply rail)
2	`BASE (B)`	Base Terminal	Base control input (Pulled down via resistor to turn transistor ON)
3	`COLLECTOR (C)`	Collector Terminal	Collector output (Connect to high-voltage load / Nixie tube anode)

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Collector-Emitter Breakdown	$V_{(BR)CEO}$	-300	—	—	V	$I_C = -1.0\text{mA}, I_B = 0$
Collector-Base Breakdown	$V_{(BR)CBO}$	-300	—	—	V	$I_C = -100\ \mu\text{A}, I_E = 0$
Emitter-Base Breakdown	$V_{(BR)EBO}$	-5.0	—	—	V	$I_E = -100\ \mu\text{A}, I_C = 0$
Collector Cutoff Current	$I_{CBO}$	—	—	-250	nA	$V_{CB} = -200\text{V}, I_E = 0$
DC Current Gain ( $h_{FE}$ )	$h_{FE}$	25	—	—	—	$I_C = -1.0\text{mA}, V_{CE} = -10\text{V}$
DC Current Gain ( $h_{FE}$ )	$h_{FE}$	40	—	200	—	$I_C = -10\text{mA}, V_{CE} = -10\text{V}$
DC Current Gain ( $h_{FE}$ )	$h_{FE}$	25	—	—	—	$I_C = -30\text{mA}, V_{CE} = -10\text{V}$
Collector Saturation Voltage	$V_{CE(sat)}$	—	—	-0.50	V	$I_C = -20\text{mA}, I_B = -2.0\text{mA}$
Base Saturation Voltage	$V_{BE(sat)}$	—	—	-0.90	V	$I_C = -20\text{mA}, I_B = -2.0\text{mA}$

Typical Application: +170V High-Side Nixie Tube Anode Multiplexer

In multiplexed Nixie tube clocks, an MPSA42 NPN pulls the base of the MPSA92 PNP LOW to switch the $+170\text{V}$ anode rail to the selected tube:

text

  +170V DC High-Voltage Boost Rail ───────────────┬─────────► [Pin 1: EMITTER]
                                                  │              MPSA92 (PNP)
                                           [ 47kΩ Pull-Up ]      [Pin 3: COLLECTOR] ──► To Nixie Tube Anode
                                                  │                 │
                                                  ├─────────► [Pin 2: BASE]
                                                  │
                                            [ 220kΩ Resistor ]
                                                  │
                                           [ Pin 3: COLLECTOR ]
  MCU GPIO (3.3V / 5V) ───[ 10kΩ Resistor ]──► Base (Pin 2) of MPSA42 (NPN)
                                           [ Pin 1: EMITTER ]
                                                  │
  System Ground (0V) ─────────────────────────────┴───────────────────────────────► Ground

Comparison: MPSA92 vs 2N5401 vs 2N3906

Parameter	2N3906	2N5401	MPSA92
$V_{CEO}$ Breakdown	$-40\text{ V}$	$-150\text{ V}$	$-300\text{ V}$ (Nixie Standard)
Max Current ( $I_C$ )	$-200\text{ mA}$	$-600\text{ mA}$	$-500\text{ mA}$
Transition Freq ( $f_T$ )	$250\text{ MHz}$	$100\text{ MHz}$	$50\text{ MHz}$
Complementary NPN	2N3904	2N5551	MPSA42

Common mistakes

Omitting the anode pull-up resistor: In high-side switching, the base of the MPSA92 must be tied to the $+170\text{V}$ rail through a pull-up resistor ( $47\text{k}\Omega \dots 100\text{k}\Omega$ ) so that the base voltage equals the emitter voltage when the lower NPN driver is turned off. Without this pull-up, leakage current will cause the Nixie tube digits to ghost or faintly glow.

Notes

Suffix Guide: MPSA92 is standard TO-92; KSP92 is the Fairchild/onsemi tape-and-reel catalog designation; MMBTA92 is the SOT-23 SMD version.

Interface	Current-Driven Base Junction
Package	TO-92 Plastic (through-hole) / SOT-23 (MMBTA92)