What is a T Flip-Flop ??? (Using Discrete Transistors)

Watch the given video.

Introduction

In this blog I explain about T flip-flop, commonly called toggle flip-flop. It is a type of flip-flop which mostly used in counters. This store 1 bit of data in it. It has a one input pin called 'T'. The input data is used to enabling the toggling. It only toggle when there present a logic '1' data as input. If data is logic '1' and then the output data toggles (1 to 0 or 0 to 1) if there present a clk. The data is stores in it until a power failure occurs. 

What is a flip-flop ?

A flip-flop is a 1 bit digital data storage unit. The latch is also done this work. But the difference between latch and flip-flop is that, In flip-flop the data input is read only when there is a clock present. So a clocked latch is called a flip-flop. The clock is a enabling mechanism. That is the data only passes to the latch when a active clock is present in clock pin. The clock triggering is different types. Edge triggering and level triggering. In level triggering the data passes in the entire active clock pulse. But in the edge triggered flip-flop the data passes only at the active level shifting instant. So, the edge triggering is used in most of the digital circuits.

The circuit diagram is given below,

Circuit Explanation

Consider the above circuit diagram. For a beginner, it is little bit complicated. But in reality it is not. It is a simple one. It is similar to the D flip-flop circuit. Basically a T flip-flop is made by connecting the 'Data In' of D flip-flop to the complementary output. Here I also connect the 'Data In' to the Q'. But the circuit never works. This technique is not wrong. It is the correct method, it works in flip-flop IC's. Here the problem is that, it is a discrete circuit. Observe the circuit diagram, then we see that we trying to connect the transistor base to it's on collector. This is the problem, so this doesn't work. So, I overcome this problem by connecting a capacitor in series with it. It solve that problem. Because the capacitor introduce a lag between the input and output. So it works well. But an another problem. The flip-flop is only change it's state in one time, second time it doesn't work. It is due to the charge stored in the capacitor. It is removed by connecting a resistor from output Q. Now the circuit works very well.  The rest of the circuit is explained in my previous BLOG, Which is about the D flip- flop.

Circuit Working

This works same as the previous D flip-flop. The difference only in the extra capacitor and resistor. The toggling is done in D flip-flop by providing alternate 'High' and 'Low' to the 'Data In' manually in each clock. We get a T flip-flop by automate this manual operation. So we need a 'high' data input when the output is at 'low' and a 'low' data input need when the output is at 'high'. That is we need a complement output. It is available in D flip-flop. So we connect the 'Data In' to the complementary output. So it automatically change the Data input in each clock pulses. So we get a T flip-flop from D flip-flop. The truth table is given below.

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In the given video, given the working of T flip-flop.

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For more about its making process, Please visit my instructables page. Link given below,

https://www.instructables.com/id/Flip-Flops-Using-Discrete-Transistors/

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Also I made "BCD counter using discrete components" in my new Blog. Please visit it. Link given below,

https://0creativeengineering0.blogspot.com/2019/03/4-bit-counter-using-discrete-transistor.html