Introduction

The BC327 is a PNP bipolar junction transistor housed in a TO-92 package for switching and amplification purposes. There are three pins, called emitter, base, and collector, which are mainly used for external connection with electronic circuits.

BC327 consists of three layers, with an n-doped layer sandwiched between two p-doped layers. The n-doped layer is negatively charged, while the p-doped layer is positively charged.

The transistor contains an 800mA collector current, so it can be easily used to drive a variety of heavy loads.

Collector dissipation is 625mW, while the maximum current gain is 630, making it a suitable choice for audio amplification purposes.

In this video we make a Powerful amplifier Using common Transistors BC337 and BC327 

Catalog

Ⅰ What is BC327 PNP Transistor?

BC327 is a general-purpose PNP Transistor, the base of which needs to be connected to the ground, to turn on the transistor. This transistor is available in various versions and is manufactured by many different companies, that’s why the gain of the transistor may vary depending upon the version of the transistor. So, it's recommended to check out the datasheet of the device before proceeding with the application and the datasheet for this specific transistor can be found at the bottom of the page.

When the transistor is turned off, we can see a positive voltage on the transistor's base, if we measure the voltage between the base and the emitter. Based on the characteristics of the transistor, a minimum amount of current needs to flow out of the base to turn the transistor on and that is when a positive voltage appears on the base, leakage current starts to flow from the base to the ground. The characteristic curve below shows that a minimum of -10mA current needs to flow through the base to flow -300mA of collector current.

The below diagram shows the correlation between base current and collector current.

Figure1-correlation between base current and collector current

Ⅱ BC327 Pinout

Figure2-bc327 pinout

Ⅲ BC327 Pinout Configuration

Ⅳ BC327 CAD Model

BC327 Symbol

Figure3-BC327 Symbol

BC327 Pinout

Figure4-BC327 pinout

BC327 3D Model

Figure5-BC327 3D Model

Ⅴ Package Type and Dimensions

If you are designing a PCB or Perf board with this component, then the following picture from the Datasheet will be useful to know its package type and dimensions.

Figure6-package type and dimensions

Ⅵ BC327 Features

• Bi-Polar, High Voltage PNP Transistor
• DC Current Gain (hFE) is 250 ~ 630
• Continuous Collector current (IC) is -800mA
• Base-Emitter on Voltage -1.2V
• MAX Base- Emitter Voltage (VBE) is -5V
• Collector-Emitter Voltage (VCE) is -45V
• Available in To-92 Package
• Switching and Amplifier Applications
• Suitable for AF-Driver Stages and Low-Power Output Stage
• Compliment to BC337/BC338

1. Voltage Specification

The terminal voltage specification of the BC327 transistor is -30V and -45V collector to emitter voltage and -5V emitter to base voltage, the voltage specification shows that it is a general-purpose device.

The collector-to-emitter saturation voltage is -0.7V, which is the switching voltage of the BC327 transistor, which is always less than the base voltage.

The overall voltage specification of the BC327 transistor shows that it is a general-purpose transistor and is used a lot in the example circuit.

2. Current Specification

The collector current value is -800mA, and the current value of the BC327 transistor shows that it is a common minimum load device.

The current values of the BC327 transistors indicate that they are more useful in driver and switching applications.

3. Dissipation Specification

The power dissipation of the BC327 transistor is 625mW, which is the power dissipation of the device.

4. Current Gain

The BC327 transistors have a current gain value of 60 to 630hFE, which is why these transistors are used in low-power amplifiers and switching applications.

5. Conversion Frequency

The bandwidth transition frequency value of the BC327 transistor is 100MHz, which is the frequency range of the transistor. BC327 transistor has a low-frequency range, so audio circuit applications are low-power and projection circuits.

6. Junction Temperature

At the junction temperature of -55 to 150°C, the thermal capacity of the transistor is mainly determined by the case.

7. Thermal Resistance

The thermal resistance of the BC327 transistor case is 200°C/W.

8. Output Capacitor

The output capacitance of the BC327 transistor is 11pF.

Ⅶ What can I Replace the BC327?

1  BC327 Transistor Equivalent

Transistors such as 2N4403, BC488, BC638, 2N4402, 2N3702, BC328, BC486, etc. are the equivalent transistors of the BC327 device.

The electrical specifications of these transistors are the same as the BC327 transistors, which is why we can use them as equivalent transistors.

BC327 is a general-purpose transistor mainly used in engineering and audio amplifier applications, we need to check and verify the pin details before replacing it.

2  BC327 Complementary

BC327 PNP transistor has NPN complementary BC337, they have the same electrical specification, so we use them as complementary.

3 BC327 Triode SMD

2SA1518 (SOT-23), 2SA1519 (SOT-23), 2SA1521 (SOT-23), BC807W (SOT-323), and other chip version transistors are chip version transistors of BC327.

These transistors have different power dissipation values than the BC327 transistors, except that all electrical specifications are the same.

4  BC327 vs BC557 vs BC488  

Ⅷ BC327 Triode Working Principle

8.1 Basic Working of a Transistor

The BC327 transistor is a general-purpose PNP transistor in which holes are the primary charge carriers for the device. When the base of the transistor is grounded, the leakage current starts to flow from the base to the ground, the depletion region of the base of the transistor starts to shrink, and more and more electrons start to migrate from the collector to the emitter and enter the circuit, so the current keeps flowing flow through the circuit.

8.2  How to Use BC327 Transistor

Unlike MOSFETs, transistors are current-controlled devices, meaning they can be turned on or off by supplying the required base current (for the BC327 transistor, it's -10mA). The BC327 is a PNP transistor, which means it turns on when connected to the ground, and turns off when the base is connected to 5V.

The simulation circuit below shows the behavior of this transistor with base current applied and with no current supplied to the base.

Figure7-BC327 working principle

When we turn on a transistor by grounding the base, the transistor will remain on unless the voltage at the base of the transistor reaches more than 1.2V. The base of the transistor cannot be left floating, otherwise the transistor may be falsely triggered, causing problems in the circuit. To fix this, we need to add pull-up resistors, for example, in the example above, a 10K resistor is used to pull up the base of the transistor.

In the above example, we used the BC327 as a simple switching device and we used a small 12V motor as the load. The little button here is used to provide the trigger for the transistor and can be removed to leave a simple contact. The 10KΩ resistor is used to limit the current flowing to the base and avoid exceeding the maximum voltage allowed by the base, and the 2.1KΩ resistor is used to limit the current flowing from the base to the ground. 

8.3 Where We Can Use BC327 Transistor

Like other essential general-purpose transistors, the BC327 is also an essential transistor in your lab because it can be used in a wide variety of applications. It can be used as a switch to drive loads up to 800mA which includes high-power relays, high-power transistors, high-power LEDs, ICs, and other parts of a circuit. With -5V emitter-base voltage this transistor can also be used as the output of microcontrollers to drive a load of up to 800mA which can easily drive motors, modules, sensors, etc.

Ⅸ BC327 Application Examples

9.1 BC327 Mini Siren

The circuit is enclosed in a small plastic box that can fit in a bag or handbag. A small magnet is placed close to the reed switch and is attached to the bag wearer's hand or clothing by a string. If the bag is snatched suddenly, the magnet loses contact with the reed switch, SW1 opens, the circuit starts to oscillate, and the speaker sounds a loud alarm.

Complementary transistor pairs are wired as high-efficiency oscillators to directly drive small speakers. Low parts count and 3V battery operation allow for very compact construction.

Figure8-BC327 Mini Siren

• R1 = 330K
• R2 = 100R
• C1 = 10nF-63V
• C2 = 100uF-25V
• Q1 = BC547
• Q2 = BC327
• B1 = 3V battery or two AA batteries in series
• SW1 = read switch and a small magnet
• SPKR = 8R speaker

A speaker can be of any type; its size is limited only by the box it is packaged in. An on-off switch is not required because the standby current consumption is less than 20µA. The current draw when the alarm goes off is about 100mA. If the circuit is used as an anti-snatch bag, SW1 can be replaced with a 3.5mm mono jack, and the magnet with a 3.5mm. Mono jack plug with internal leads shorted.

Jack plugs will connect to thin wires etc. Do not power this circuit with more than 4.5V: it will not work, Q2 may be damaged, and a 3V supply is the best compromise.

9.2 BC327 Switch Circuit

The circuit is just two PNP transistors that are set to be on or off. On is like a closed switch and off is an open circuit between collector and emitter terminals. Here though one transistor is directly connected to the collector of the first transistor, so it will invert the operation of the first transistor.

When the unconnected end of the 100k resistor is connected to the negative terminal of the 7 (or 9V) battery, current will flow through the 100k to establish -0.7 across the base-emitter junction and turn on Q1. When Q1 turns on, its collector-emitter junction voltage is about -0.2V and allows current to flow through LED1. Since Vce1 is only -0.2V, this is not enough to turn on Q2, so LED2 turns off.

When the 100k resistor is connected to the ground, vbe1 is less than -0.7V, and no base current flows, so Q1 is off, so LED1 is off. However, since Q1 is off, its collector-emitter junction is open, and the voltage across LED1 and R4 is zero because no or very little current flows. The open circuit voltage at the collector-emitter junction of Q1 is about -7V, which allows the base current in Q1 to flow and turn on Q2, which turns on LED2.

Figure9-BC327 switch circuit

9.3  Car Brake Light Circuit Using BC327

In order to add some aesthetics to the car brake light circuit, 14 LEDs are needed clearly visible, safe, and beautiful. The installation format can repair itself as needed. This circuit uses an astable multivibrator to generate an oscillating frequency to make all the LEDs blink.

Figure10-car brake light circuit

When the braking voltage of the lamp is input, the power source 12V will come in, and LED6-LED9 will glow or light up. Also, the trend will flow R2 to the base of the Q1-BC327 PNP transistor and bias pin of Q2-BC327 to light up LED1-LED5 and LED11-LED14. Having R1 and R3 in there helps limit the current through the LED enough to release the brake power 12V disappearing making the LED turn off each time.

Components list:

• Q1, Q2: BC327: 50V 1A PNP transistor
• LED1-LED14: LED display
• R1, R4: 22 ohms 0.5 watts 5% resistors
• R2: 390 ohms, 0.5 watts 5% resistor
• R3: 500 ohms, 0.5 watts 5% resistor

9.4 250mW Audio Amplifier

This is a very simple three-transistor audio amplifier circuit that can deliver 250mW into an 8-ohm speaker. Complementary transistors BC337 and BC227 (Q3 and Q2) are used as the output pair.

Transistor Q1 (BC 547) acts as a preamplifier. The POT R5 can be used as a volume control. Capacitor C1 separates the DC from the audio source.

Resistor R2 ensures better stability of the amplifier. This amplifier is ideal for use as a preamp in small radios and high-power audio amplifiers.

Figure11-250mW Audio Amplifier

• JING This circuit can be powered by 9V DC.
• Assemble the circuit on the Vero board.
• K1 can be an 8-ohm speaker.
• For better performance, properly decouple input and output grounds.
• POT R5 can be used to adjust the volume.

9.5 Other Applications

• PWM drive application
• LED dimmer or flash
• switch app
• power amplifier preamplifier
• microphone preamplifier
• relay driver

Ⅹ How to Get Long-Term Performance From BC327

To get long-term good performance with this transistor in your electronic applications it is recommended to not drive a load of more than 0.8A or 800mA, not drive a load of more than -45V, and always use a suitable base resistor with the transistor. Do not store or operate this transistor in temperatures below -55 centigrade and above +150 centigrade and always check the pin configuration before placing it in the circuit.

Ⅺ BC327 PNP Transistor PDF

BC327 PNP Transistor Datasheet