B772 (2SB772) — -30V -3A Low-Saturation Medium-Power PNP BJT (TO-126)

Overview

The B772 (officially 2SB772) is a -30V -3A medium-power silicon PNP bipolar junction transistor manufactured by NEC, Toshiba, UTC (Unisonic), and STMicroelectronics. Housed in a through-hole TO-126 (SOT-32) plastic package with a central mounting hole, it is renowned for its extraordinarily low saturation voltage.

Providing a continuous collector current rating of $-3.0\text{A}$ ( $-7.0\text{A}$ pulsed peak) and a collector saturation voltage ( $V_{CE(sat)}$ ) as low as $-0.3\text{V} \dots -0.5\text{V}$ at $-2.0\text{A}$ , the B772 operates with minimal conduction losses. Serving as the official PNP complement to the D882 (2SD882), the B772 is ubiquitous in Asian consumer electronics, found in low-voltage emergency lamp inverters, discrete audio power amplifiers, camera flash triggers, linear voltage regulator pass elements, and toy RC car bidirectional motor drivers.

Quick reference


Transistor Type	Medium-Power Low-Saturation Silicon PNP BJT
Package	TO-126 / SOT-32 (3-pin through-hole with mounting hole) / SOT-89
Collector-Emitter Breakdown ( $V_{CEO}$ )	$-30\text{ V}$ max
Collector-Base Breakdown ( $V_{CBO}$ )	$-40\text{ V}$ max
Continuous Collector Current ( $I_C$ )	$-3.0\text{ A}$ max ( $-7.0\text{ A}$ pulsed peak)
Base Current ( $I_B$ )	$-0.5\text{ A}$ max
Collector Saturation ( $V_{CE(sat)}$ )	$-0.3\text{ V}$ typ / $-0.5\text{ V}$ max at $I_C = -2.0\text{A}, I_B = -200\text{mA}$
DC Current Gain ( $h_{FE}$ )	$60$ to $400$ (Classified by gain rank: R, Q, P, E)
Transition Frequency ( $f_T$ )	$80\text{ MHz} \dots 100\text{ MHz}$
Power Dissipation ( $P_D$ )	$10.0\text{ Watts}$ ( $T_C = 25^\circ\text{C}$ with heatsink) / $1.0\text{ W}$ in free air
Complementary NPN Pair	D882 (2SD882)

Pinout (TO-126 Package - Japanese JIS Standard)

Looking at the printed front face of the TO-126 package with leads pointing downward:

text

        ┌───────────────┐
        │   O [Mount]   │
        ├───────────────┤
        │     B772      │
        └─┬─────┬─────┬─┘
          1     2     3
          E     C     B

Pin	Name	Type	Description
1	`EMITTER (E)`	Emitter Terminal	Emitter (Connect to positive power supply rail)
2	`COLLECTOR (C)`	Collector Terminal	Collector (Connected to switched load; internally bonded to rear metal tab)
3	`BASE (B)`	Base Terminal	Base control input (Driven with base current via series resistor)

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Collector-Emitter Breakdown	$V_{(BR)CEO}$	-30	—	—	V	$I_C = -10\text{mA}, I_B = 0$
Collector-Base Breakdown	$V_{(BR)CBO}$	-40	—	—	V	$I_C = -100\ \mu\text{A}, I_E = 0$
Emitter-Base Breakdown	$V_{(BR)EBO}$	-6.0	—	—	V	$I_E = -10\ \mu\text{A}, I_C = 0$
Collector Cutoff Current	$I_{CBO}$	—	—	-1.0	µA	$V_{CB} = -30\text{V}, I_E = 0$
DC Current Gain ( $h_{FE}$ )	$h_{FE}$	60	—	400	—	$I_C = -1.0\text{A}, V_{CE} = -2.0\text{V}$
Collector Saturation Voltage	$V_{CE(sat)}$	—	-0.30	-0.50	V	$I_C = -2.0\text{A}, I_B = -200\text{mA}$
Base Saturation Voltage	$V_{BE(sat)}$	—	-1.00	-2.00	V	$I_C = -2.0\text{A}, I_B = -200\text{mA}$
Transition Frequency	$f_T$	50	80	—	MHz	$I_C = -500\text{mA}, V_{CE} = -5.0\text{V}$

$h_{FE}$ Classification Ranks

Rank	$h_{FE}$ Range	Application Suitability
R	$60 \dots 120$	High-power switching
Q	$100 \dots 200$	General-purpose power switching
P	$160 \dots 320$	Audio amplifier drivers & general DIY kits
E	$200 \dots 400$	High-gain audio preamplifiers & low-current drive

Comparison: B772 vs BD140 vs TIP42C

Parameter	B772	BD140	TIP42C
$V_{CEO}$ Voltage	$-30\text{ V}$	$-80\text{ V}$	$-100\text{ V}$
Max Current ( $I_C$ )	$-3.0\text{ A}$	$-1.5\text{ A}$	$-6.0\text{ A}$
Saturation $V_{CE(sat)}$	$-0.3\text{ V}$ at 2A (Ultra-Low)	$-0.5\text{ V}$ at 0.5A	$-1.5\text{ V}$ at 6A
Package	TO-126 (Compact)	TO-126 (Compact)	TO-220 (Large)

Common mistakes

Exceeding the -30V breakdown limit: The B772 is designed for low-voltage ( $3.7\text{V} \dots 24\text{V}$ ) high-current circuits. Do not use in $36\text{V} \dots 48\text{V}$ systems; use the BD140 instead.
Operating without a heatsink at 2A+ loads: Although $V_{CE(sat)}$ is low, continuous operation above $1.0\text{A}$ requires mounting the TO-126 tab to a heatsink.

Notes

Naming Convention: 2SB772 is the full Japanese Industrial Standard (JIS) part number; B772 is the standard top-mark abbreviation printed on the physical package.

Interface	Current-Driven Base Junction
Package	SOT-32 / TO-126 (3-pin through-hole with mounting hole) / SOT-89