Most of the designers provide commercial as well as extensive temperature ranges. It is a logical family consisting completely of transistors. It employs a transistor with multiple emitters. Commercially it starts with the 74 series like the , 74S86, etc. It was built in by James L Bui and commercially used in logic design in TTLs are classified based on the output. The main feature is that its output is 0 when low and floating when high.
Usually, an external Vcc may be applied. Transistor Q1 behaves as a cluster of diodes placed back to back. With any of the input at logic low, the corresponding emitter-base junction is forward biased and the voltage drop across the base of Q1 is around 0. Thus the output is either floating or Vcc, i. High level. Similarly, when all inputs are high, all base-emitter junctions of Q1 are reverse biased and transistor Q2 and Q3 get enough base current and are in saturation mode.
The output is at logic low. Totem Pole means the addition of an active pull up the circuit in the output of the Gate which results in a reduction of propagation delay. Logic operation is the same as the open collector output. The use of transistors Q4 and diode is to provide quick charging and discharging of parasitic capacitance across Q3. The resistor is used to keep the output current to a safe value.
TTL ICs mostly start with the 7 series. It has 6 subfamilies given as:. Basically, this means that output voltage of the device driving HIGH will always be at least 2. You will also notice that there is cushion of 0. This is sometimes referred to as noise margin. This means that a device trying to send out a logic 0 will always be below 0. So, any input signal that is below 0. What happens if you have a voltage that is in between 0.
Well, your guess is as good as mine. Honestly, this range of voltages is undefined and results in an invalid state, often referred to as floating.
Need Help? A transistor-transistor logic device makes use of transistors with multiple emitters in gates having multiple inputs. There are different sub-categories or families for transistor-transistor logic, such as:. One of the biggest benefits of using transistor-transistor logic is the relative easiness in interfacing different circuits and the ability to produce complex logic functions.
This is mainly due to good noise margins as well as guaranteed voltage levels. Transistor-transistor logic is largely immune to damage from static electricity discharges, unlike CMOS, and are also relatively inexpensive compared to CMOS. One major disadvantage of transistor-transistor logic is its high current consumption. The heavy current demands of transistor-transistor logic can lead to improper functioning due to switching of output states.
Even with different transistor-transistor logic versions that are less current consuming, they are all still competitive to CMOS. However, transistor-transistor logic is still used in applications as they are fairly robust and the gates are relatively inexpensive. By: Justin Stoltzfus Contributor, Reviewer. By: Satish Balakrishnan.
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