Since the load resistor is high, we can start by selecting a medium to high collector resistor, like for example 1000 Ohms. The point is that we cannot have large collector resistor if the load resistor is low. The higher the collector resistor, the higher the voltage amplification of the amplifier. We will select one collector resistor with an educative guess, taking into account the load resistor R L. We can start the design by estimating the RC resistor. First, let's design the circuit schematic: We will use the same value for hfe as well (AC Current gain). The transistor is a BC338 with a typical h FE=250 (DC current gain).
3 resistor npn transistor amplifier generator#
The internal resistor of the signal generator is not significant so we leave it out of our calculations for now. The DC biasing voltage is 12 Volts and the input signal is 10 mVolts p-p. This amplifier will drive a high impedance load (10 Kohms). Let's see how we can design such an amplifier. If you are designing a PCB or Perf board with this component then the following picture from the S8050 transistor Datasheet will be useful to know its package type and dimensions.As said, this setup achieves maximum voltage amplification ratio. A simple circuit diagram of the Class B amplifier with the using the S8050 is shown below. Like here the NPN transistor will be S8050 and its equivalent PNP transistor will be S8550. By complimentary it means that we need a NPN transistor and its equivalent PNP transistor. It is very simple to construct and requires two identical complimentary transistors operate. So let us discuss how that is done.Ī push pull amplifier, commonly known as Class B amplifier is type of multistage amplifier commonly used for audio amplification of loudspeakers. When base current is removed the transistor becomes fully off, this stage is called as the Cut-off Region.Īs mentioned in the features of the S8050 transistor is commonly used in push pull configuration with Class B amplifier. This stage is called Saturation Region and the typical voltage allowed across the Collector-Emitter (VCE) or Collector-Base (VCB) could be 20V and 30V respectively. When this transistor is fully biased then it can allow a maximum of 700mA to flow across the collector and emitter. To bias a transistor we have to supply current to base pin, this current (IB) should be limited to 5mA. The maximum amount of current that could flow through the Collector pin is 700mA, hence we cannot drive loads that consume more than 700mA using this transistor. However at a normal operating collector current the typical value of gain will be 110. Since it is very high it is normally used for amplification purposes.
It has a maximum gain value of 400 this value determines the amplification capacity of the transistor normally S8050. S8050 is a NPN transistor hence the collector and emitter will be left open (Reverse biased) when the base pin is held at ground and will be closed (Forward biased) when a signal is provided to base pin. Note: Complete Technical Details can be found in the S8050 datasheet given at the end of this page. High Used in push-pull configuration doe Class B amplifiers.Continuous Collector current (IC) is 700mA.Low Voltage, High Current NPN Transistor.
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