Need help to understand this circuit

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In summary, the circuit of JDM programmer utilizes a transistor, Q2, which receives voltage from the programmed micro and the RS232 port of a computer. Q2 operates as both a common base amplifier and an emitter follower, depending on the process being performed. The exact processes involved can be understood by knowing the programming software.
  • #1
aruna1
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this is the circuit of JDM programmer.
I'm trying to understand how Q2 works here.coz only base of Q2 get a voltage and emitter or collector is not connected to power supply,

there is a description about this circuit,but I can't understand that description.

here is the circuit

http://img17.imageshack.us/img17/322/newpic22.gif [Broken]

and this is the description
http://www.jdm.homepage.dk/newpic7.htm"
 

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  • #2
The Micro being programmed can supply voltage or connect the RB7 port of the chip to ground.

The connections at the right hand side of the diagram refer to a serial RS232 port on a computer which can also supply power.

So, the transistor Q2 gets its voltages from these sources and it operates sometimes as a common base amplifier and sometimes as an emitter follower, which is a neat trick.

You would have to know the programming software to work out the exact processses involved, but the description seems to describe the function of this transistor adequately.
 
  • #3


I can help you understand this circuit by breaking down its components and their functions.

Firstly, this is a circuit for a JDM programmer, which is used for programming microcontrollers. The main function of this circuit is to provide a high voltage (around 13V) to the programming pins of the microcontroller.

Now, let's look at Q2. It is a transistor, specifically a PNP transistor, and its main function in this circuit is to amplify the voltage provided by Q1. Q1 is a voltage regulator that takes in a higher voltage (usually 12V) and outputs a stable 5V. This 5V is then amplified by Q2 to around 13V.

But you may be wondering why only the base of Q2 is connected to the voltage regulator and not the emitter or collector. This is because Q2 is acting as a switch in this circuit. When the base of Q2 receives a voltage from Q1, it allows current to flow from the collector to the emitter, thus providing the 13V needed for programming the microcontroller.

The description you provided mentions that Q2 is being used in "common emitter mode." This means that the emitter of Q2 is connected to ground and the collector is connected to the programming pins of the microcontroller. This allows for a common ground reference between the programming circuit and the microcontroller.

I hope this explanation helps you understand the circuit better. If you have any further questions, please don't hesitate to ask.
 

1. What is the purpose of this circuit?

The purpose of this circuit is to control the flow of electricity to power a specific device or perform a specific function.

2. How does this circuit work?

This circuit works by using a combination of components such as resistors, capacitors, and transistors to regulate the flow of electricity and create a desired output.

3. What are the different components used in this circuit?

The components commonly used in circuits include resistors, capacitors, diodes, transistors, and integrated circuits. These components work together to control the flow of electricity and create specific functions.

4. What is the difference between a series circuit and a parallel circuit?

A series circuit is a circuit where the components are connected in a single loop, so the current flows through each component in order. A parallel circuit is a circuit where the components are connected in multiple branches, so the current can flow through each branch separately.

5. How can I troubleshoot this circuit if it is not working?

If the circuit is not working, you can troubleshoot by checking each component to ensure it is connected properly and functioning correctly. You can also use a multimeter to measure the voltage and current at different points in the circuit to identify any potential issues.

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