TIP121 Darlington transistor
TIP121 specification
- TIP121 is a medium power epitaxial NPN Darlington pair transistor device
- Collector to emitter voltage is 80V
- Collector to base voltage is 80V
- Emitter to base voltage is 5V
- Collector current is 5A
- Pulsed collector current is 8A
- Base current is 120mA
- Power dissipation is 65W
- DC current gain is 1000hFE
- Junction temperature & operation temperature is between -65 to +150℃
- Collector to emitter saturation voltage (VCE (SAT)) is 2V to 4V
- Thermal resistance is 92℃/W
- Output capacitance is 200pF
- Low voltage transistor device
- Low saturation voltage
TIP121 transistor Pinout
| Pin Number | Pin Name | Description |
| 1 | Base | The base is the trigger for the transistor |
| 2 | Collector | Current flows through the collector |
| 3 | Emitter | Current flows through the emitter |
TIP121 transistor package
TIP121 is a medium power Darlington transistor device used for heavy applications, this is why they had a TO-220AB transistor package.
The TO-220AB package is made with a combination of two materials such as metal and epoxy/plastic material. The outer cover is made with epoxy which is more heat resistant and the back side metal covering is used to transfer the heat towards the heat sink.
TIP121 Darlington transistor electrical specification description
In this section we try to describe the electrical specifications of the TIP121 transistor device, this is useful for a better understanding of this device.
Voltage specs
The terminal voltage specs of the TIP121 transistor are collector to base voltage and collector to emitter voltage is 80V and emitter to base voltage is 5V.
The collector to emitter saturation voltage is 2V to 4V, it is the voltage value of region switching and this value is always less than the base voltage.
Overall voltage specifications of the TIP121 transistor state that, it is a medium power device mainly used for low power applications.
Current specs
The collector current specs of the TIP121 transistor is 5A, the load capacity is under 5A.
The pulsed collector current is 8A, it is the current value at a special condition where the temperature values of the device are low.
The base current value is 120mA, it is the current value used to trigger the TIP121 transistor device.
Dissipation specs
The power dissipation value of the TIP121 transistor is 65W, the device dissipation mainly depends on the transistor package and overall capacity.
Current gain specs
The current gain value of TIP121 is 1000hFE, the DC current value shows that it devise mainly used for amplifier applications.
Junction temperature
The junction temperature & operating temperature values are -65 to 150℃, and the TIP121 is a Darlington power transistor.
Thermal resistance
The thermal resistance of the TIP121 transistor case is 1.92℃/W
TIP121 Darlington transistor DATASHEET
If you need the datasheet in pdf please click this link
TIP121 transistor equivalent
The TIP121 transistor had equivalent transistors such as 2N6530, 2N6532, 2N6043, TIP122, BDW41, 2SD2495, BDW43, MJF122, and TIP101. Each of these transistors is a Darlington transistor mainly used for similar applications.
The electrical specifications of these transistors are almost the same, so we use them as the replacement for the TIP121 transistor.
We need to check and verify the PINOUT details of these devices become the replacement, this is because all of them as power transistor devices.
TIP121 Darlington transistor complementary
The TIP121 NPN Darlington transistor device had a complimentary pair of TIP126 PNP transistors.
TIP121 vs TIP101
In the below, we try to compare the electrical specifications of TIP121 vs TIP101 transistors, this is a better way to know about both these transistors, and also we can use them in circuits.
| Characteristics | TIP121 | TIP101 |
|---|---|---|
| Collector to base voltage (VCB) | 80V | 80V |
| Collector to emitter voltage (VCE) | 80V | 80V |
| Emitter to base voltage (VEB) | 5V | 5V |
| Collector to emitter saturation voltage (VCE (SAT)) | 2V to 4V | 2 to 2.5V |
| Collector current (IC) | 5A | 5A |
| Power dissipation | 65W | 2W |
| Junction temperature (TJ) | -65 to +150°C | -65 to +150°C |
| Gain (hFE) | 1000hFE | 1000 to 20000hFE |
| Output capacitance | 200pF | 20pF |
| Package | TO-220AB | TO-220 |
The voltage specs of TIP121 and TIP101 is been much similar, only the saturation voltage is less at the TIP101 transistor.
The DC current gain value of TIP101 is higher, so the amplification factor is TIP121 is less than TIP101.
The power dissipation value of the TIP121 transistor is higher than the TIP101 transistor.
TIP121 Darlington transistor applications
- Linear switching applications
- Low-speed switching applications
- Motor driver applications
- Battery charger applications
- Audio power amplifier applications
- Preamp circuits
- Output circuits of Microcontroller
TIP121 transistor Darlington characteristics curves
The figure shows DC current gain characteristics of the TIP121 transistor, the graph is plotted with DC current gain vs collector current.
At a fixed collector to an emitter voltage value, the DC current gain of the transistor increases from a medium value towards a higher limit like a parabolic shape and drops at the end.
The figure shows the collector to emitter saturation voltage characteristics of the TIP121 transistor, the graph is plotted with the collector to emitter saturation vs collector current.
At a fixed collector current, the saturation voltage value increases from the lowest value to become constant and then increases after a point like an inverted parabolic.
