# How to read the datasheet (electrical characteristics) of a bias resistor built-in transistor (BRT)

The key electrical characteristics of the BRT are explained below.
In the datasheet, electrical characteristics are specified at an ambient temperature (Ta) of 25°C, unless otherwise noted. Be sure to refer to graphs in addition to the values shown in the Electrical Characteristics table.

1. Input voltage (ON), VI(ON)
VI(ON) is the input voltage required for a transistor to pass the specified current under the specified conditions. To turn on the BRT without fail, it is necessary to apply a voltage higher than the maximum input voltage (ON) (VI(ON)) across the base (B) and emitter (E) terminals.
The IC – VI(ON) curves indicate that VI(ON) decreases as temperature increases.

Input on voltage by products
Characteristic Symbol

Test

Circuit

Test Condition Min Typ. Max Unit
Input voltage (ON) RN1401 VI (ON) VCE = 0.2 V, IC = 5 mA 1.1 2.0 V
RN1402 1.2 2.4
RN1403 1.3 3.0
RN1404 1.5 5.0
RN1405 0.6 1.1
RN1406 0.7 1.3

2. Input voltage (OFF), VI(OFF)
VI(OFF) is the input voltage required to meet the conditions under which a BRT is defined as off. To turn off the BRT without fail, it is necessary to apply a voltage lower than the minimum input voltage (OFF) (VI(OFF)) across the base (B) and emitter (E) terminals. As is the case with VI(ON), VI(OFF) decreases as temperature increases.

Input off voltage by products
Characteristic Symbol Test Circuit Test Condition Min Typ. Max Unit
Input voltage (OFF) RN1401 to 1404 VI (OFF) VCE = 5 V, IC = 0.1 mA 1.0 1.5 V
RN1405, 1406 0.5 0.8

3. Collector-emitter saturation voltage, VCE(sat)
VCE(sat) is the collector-emitter voltage of the BRT when it is operating in the saturation region at the specified current. The VCE(sat) – IC curves indicate that VCE(sat) increases as temperature increases.

Collector-emitter saturation voltage by products
Characteristic Symbol Test Circuit Test Condition Min Typ. Max Unit

Collector-emitter

saturation voltage

RN1401 to 1406 VCE(SAT) IC = 5 mA, IB = 0.25 mA 0.1 0.3 V

4. Input resistor, R1
R1 is the value of a resistor in series with the base terminal of the BRT. In the case of the BRTs shown below, there is ±30% variation in R1. R1 affects VI(ON) and other characteristics. R1 decreases at a rate of roughly 0.2%/°C.

Input resistor by products
Characteristic Symbol

Test

Circuit

Test Condition Min Typ. Max Unit
Input resistor RN1401 R1 3.29 4.7 6.11
RN1402 7 10 13
RN1403 15.4 22 28.6
RN1404 32.9 47 61.1
RN1405 1.54 2.2 2.86
RN1406 3.29 4.7 6.11

5. Resistor ratio, R1/R2
The resistor ratio (R1/R2) is the ratio of the R1 resistance to the R2 resistance. In the case of the BRTs shown below, there is ±10% variation in R1/R2. The value of the base-emitter resistor (R2) is not specified separately. Instead, the resistor ratio (R1/R2) is specified since it is more important.

Resistor ratio by products
Characteristic Symbol

Test

Circuit

Test Condition Min Typ. Max Unit
Resistor ratio RN1401 to 1404 R1/R2 0.9 1.0 1.1
RN1405 0.0421 0.0468 0.0515
RN1406 0.09 0.1 0.11
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