1. It as been determined that no problems, such as degradation or destruction, will arise from use.

2. In the case of an NPN transistor B is symmetrical with C, and E with N. Therefore, C and E can be used as a transistor, even when connected in reverse. In this case current will flow from E to C.

3. The following are characteristics of transistors connected in reverse
• Low h_FE (approx. 10% of the value of the forward direction)
• Low voltage resistance (around 7-8V, about the same as V_EBO) The voltage may even be lower (below 5V) in some standard transistors (Please consider that excessively low voltage resistance may result in breakdown and degradation of characteristics)
• V_CE(sat) and V_BE(ON) should not change much

Definition: When voltage is supplied to a transistor the element will begin to generate heat due to power loss based on current flow, particularly when the junction temperature Tj reaches the absolute maximum value (150ºC).
Calculation Method (Where △Tx is the amount of temperature rise when power Px is supplied)

In this case Pc, Ta, △Tx, and Px can be directly derived from measurement results. Tj is the only value that cannot be directly derived. Therefore, the following shows how to measure V_BE, from which we can determine the junction temperature Tj.

In silicon transistors V_BE will vary based on the temperature.

Therefore, the junction temperature can be inferred by measuring V_BE.
From the measurement circuit at left (Diagram 1) the package power Pc(max) is applied to the transistor. (In the case of a 1W transistor, the conditions for supply are V_CB=10VI_E=100mA)

As seen in Diagram 2:
• V_BE1 is measured as the initial value of V_BE
• When power is suppled to the transistor heat saturation will occur at the junction
• The value of V_BE after will be V_BE2

From these results: △V_BE=V_BE2-V_BE1

Here a silicon transistor will have a fixed temperature coefficient based on temperature, which is around -2.2mV/C. (Darlington transistors: -4.4mV/C). Therefore, △V_BE from the supplied power can be derived from the rise in junction temperature using the following formula:

f_T: Gain bandwidth indicates the maximum operating frequency of the transistor.
At this time the collector current ratio with the base current is limited to 1 (h_FE=1)

When the base input frequency (operating frequency) is increased the h_FE is reduced. At this time when h_FE becomes 1, the operating frequency f_T is referred to as the gain bandwidth. f_T signifies the operating frequency limit. However, in actuality for operation the value will be about 1/5th to 1/10th that of f_T.

f: Depends on the measurement equipment. Reference frequency for measurement.
V_CE: optional setting - standard value is normally used for ROHM products.
Ic: optional setting - standard value is normally used for ROHM products.

When supplying a flyback voltage to the collector C a voltage greater than Vz is supplied between C and B, resulting in current flow through the Zener diode and Transistor ON. -

This flyback energy is absorbed by DTDS14GP. -

At this time a current Iz equivalent to 1/h_FE will flow through the Zener diode. In other words, for an Ic (flyback) of 1A and when using the DTDS14GP, which has an h_FE of 1000: Iz=1A/1000=1mA.