<< Chapter < Page Chapter >> Page >
SSPD_Chapter 7_Part 3_Basic Electrical Properties of MOSFET_continued 8 gives the configuration of BiCMOS inverter and its optimized version.

SSPD_Chapter 7_Part 3_Basic Electric Properties of MOSFET_Continued_8

7.3.15. BiCMOS Inverters.

In the output stage where loads have to be driven, CMOS Logic Gates themselves cannot give adequate current for drivng the loads. In these circuits buffer BJT are added as shown in Figure The inverted logic operation is carried out as shown in Table

Table The Inverted Logic Operation of BiCMOS inverter.

Input Q1 Q2 Q3 Q4 Vout
LOW(GND) off On and Q2 sources current to charge C L to 5V through a low impedance path provided by on BJT Q2 off on HIGH=5-V BE (on)
HIGH(5V) On and Q1 sinks current thereby discharging C L through low impedance path provided by on BJT Q1 off on off LOW = V CE (sat)

The characteristics of BiCMOS Inverter.

i.Logic levels are close to bus voltages;

ii.High input impedance;

iii.Low output impedance;

iv. It has high current drive capability and occupies a relatively small area;

v. It has large Noise Margin.

But this configuration has high standby dissipation under I/P = HIGH condition since Q1 and Q3 provide a low impedance path from Positive Bus to GND bus.

Also this configuration has no path for turning off the BJT when required.This slows the switching operation. Hence we go for improved circuit configuration.

In Figure we have removed the direct dc path from Positive Bus to GND through Q3 and Q1 but when Vin = HIGH, Vout ≠ V CE (sat) which is 0.2V but Vout = V BE (on) = 0.7V. Hence output swing is reduced from full 5V to about 4V.

Also BJTs still donot have a discharge path for their base currents during turn off of the respective BJT. So a third configuration is given in Figure

In the improved version shown in Figure two resistances R1 and R2 are introduced in the discharge paths of the bases of the BJTs , Q1 and Q2. Because of the resistances, the logic levels are improved and hence voltage swing is optimized. The resistances also speed up the switching of the transistors.

Though this is an improved version of BiCMOS Inverter from IC technology point of view it is impractical because passive chip resistances occupy large real estate area and suitable values are difficult to realize. Hence chip resistances are replaced by MOS transistors as shown in Figure

In Figure, the function of R1 is fulfilled by Q5 and function of R2 is fulfilled by Q6. The states of different transistors during Inverted Logic Operation are given in Table

Table Inverted Logic Operation of the optimized version ogf BiCMOS.

Vin Q1 Q2 Q3 Q4 Q5 Q6 Vout
HIGH SAT OFF ON OFF ONThis provides the discharge path for the base current of Q2 which was ON previously OFF LOW=V CE (sat)
LOW OFF ON OFF ON OFF ONThis provides the discharge path for the base current of Q1 which was in SAT previously HIGH

This circuit offers enormous advantages where high load current sourcing and sinking are required. Whenever Video Monitors or Speakers are to be driven there we require BiCMOS interface at the output.

Questions & Answers

what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
how can I make nanorobot?
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Solid state physics and devices-the harbinger of third wave of civilization. OpenStax CNX. Sep 15, 2014 Download for free at http://legacy.cnx.org/content/col11170/1.89
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Solid state physics and devices-the harbinger of third wave of civilization' conversation and receive update notifications?