Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

What is bandgap and why is it important in analog design?

Status
Not open for further replies.

no_mad

Full Member level 5
Joined
Dec 10, 2004
Messages
272
Helped
30
Reputation
60
Reaction score
11
Trophy points
1,298
Location
Naboo
Activity points
2,358
Hi,

My knowledge in analog design is very limited. Thus, can someone please tell me what is a bandgap? why is it so important in Analog Design (mix signal)?

Highly appreciated

Thanx in advance,
-no_mad
 

surianova

Advanced Member level 1
Joined
Sep 1, 2004
Messages
411
Helped
30
Reputation
60
Reaction score
8
Trophy points
1,298
Location
ASIA
Activity points
3,276
dtmos band gap reference

bandgap generate output that is independent of temperature. It is very
important in analog design as a reference voltage. For example, in voltage
regulator design, common mode feedback , you need a reference voltage constant
across temperature.
 

jinxingsun

Member level 5
Joined
Aug 28, 2005
Messages
84
Helped
5
Reputation
10
Reaction score
1
Trophy points
1,288
Activity points
1,876
bandgap voltage reference 1.205

The bandgap in very important in A/D and D/A.
 

nagula suresh

Junior Member level 3
Joined
Jan 23, 2005
Messages
29
Helped
3
Reputation
6
Reaction score
2
Trophy points
1,283
Activity points
270
bandgap voltage 1.205

accuracy of the data converters depends on the precision reference voltage.,
bandgap reference voltage is temperature and process independent.,
thus it will be used in A/D and D/A converters.
 

huojinsi

Full Member level 5
Joined
Jan 21, 2005
Messages
256
Helped
25
Reputation
50
Reaction score
6
Trophy points
1,298
Activity points
2,216
recombination third body conserve momentum

Normally, the band-gap we say means the band-gap voltage of silicon, and it equates 1.205V, furthermore it has very low temperature coefficient.
In analog design, we often use Band-gap voltage to generate voltage reference. So for Band-gap voltage reference, the very low temperature coefficient is its most keypoint, certainly also contain its precision characteristic.
 

Chethan

Full Member level 3
Joined
Jul 11, 2005
Messages
173
Helped
20
Reputation
40
Reaction score
12
Trophy points
1,298
Location
Bangalore
Activity points
2,841
silicon band-gap temperature coefficient

huojinsi said:
Normally, the band-gap we say means the band-gap voltage of silicon, and it equates 1.205V, furthermore it has very low temperature coefficient.
In analog design, we often use Band-gap voltage to generate voltage reference. So for Band-gap voltage reference, the very low temperature coefficient is its most keypoint, certainly also contain its precision characteristic.

Hi Houjinsi,
i agree that the bandgap voltage of silicon is around 1.2V. But how is it related to the reference voltage circuit. I have seen some bandgap references having a different output voltage other than 1.205V. can u please explain. any material regarding this would be welcome.

thanx in advance
chethan
 

jc2

Member level 3
Joined
Mar 5, 2005
Messages
64
Helped
3
Reputation
6
Reaction score
1
Trophy points
1,288
Activity points
1,793
what is bandgap

Chetan, for achieving a voltage reference with a low temperature coefficient you need to add a CTAT(Complementary to absolute temperature) voltage with a PTAT(Proportional to absolute temperature) voltage. The CTAT voltage usually is the forward bias voltage across a p-n diode; this voltage at 0ºK is almost equal to the bandgap voltage of the material at 0ºK (silicon≈1.2V); then the output voltage of the bandgap reference is almost the bandgap voltage at 0ºK. See the figure that i uploaded.

A bandgap reference circuit can generate other voltages:
You can scale the output voltage with resistors.
You can use DTMOS devices.
You can use other material with a different bandgap voltage at 0ºK (Ge≈0.6V) for making your circuit.
 

yuzman

Newbie level 4
Joined
Mar 10, 2006
Messages
5
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,315
bandgap pvt independent

bandgap is essential in most analog applications.A good bandgap provides very stable voltage reference with PVT independent.
 

safwatonline

Advanced Member level 4
Joined
Nov 19, 2005
Messages
1,347
Helped
219
Reputation
438
Reaction score
47
Trophy points
1,328
Location
EGYPT
Activity points
9,059
complementary to absolute temperature -patent

jc2 said:
You can use DTMOS devices.
hello jc2,
i was hoping more info about DTMOS devices.
thnx and regards,
a.safwat
 

mircea

Member level 1
Joined
Sep 7, 2005
Messages
38
Helped
4
Reputation
8
Reaction score
2
Trophy points
1,288
Location
Romania
Activity points
1,598
what is bandgap?

In solid state physics and related applied fields, the band gap is the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. It is often spelled "bandgap".
There is virtually no bandgap in most metals, but a very large one in an insulator (dielectric). In a semiconductor, the bandgap is small. Technically, the bandgap is the energy it takes to move electrons from the valence band to the conduction band.
A bandgap reference voltage is just a voltage reference based on this property.

rgds,
M
 

kishansaralaya

Newbie level 2
Joined
Mar 10, 2006
Messages
2
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,283
Activity points
1,312
what is band gap

In semiconductor physics, a direct bandgap means that the minimum of the conduction band lies directly above the maximum of the valence band in momentum space. In a direct bandgap semiconductor, electrons at the conduction-band minimum can combine directly with holes at the valence band maximum, while conserving momentum. The energy of the recombination across the bandgap will be emitted in the form of a photon of light. This is radiative recombination, also called spontaneous emission. In indirect bandgap semiconductors such as crystalline silicon, the momentum of the conduction band minimum and valence band maximum are not the same, so a direct transition across the bandgap does not conserve momentum and is forbidden. Recombination occurs with the mediation of a third body, such as a phonon or a crystallographic defect, which allows for conservation of momentum. These recombinations will often release the bandgap energy as phonons, instead of photons, and thus do not emit light. As such, light emission from indirect semiconductors is very inefficient and weak.
 

zenisle

Full Member level 2
Joined
Sep 11, 2005
Messages
129
Helped
4
Reputation
8
Reaction score
2
Trophy points
1,298
Activity points
1,987
What is bandgap?

bandgap reference circuit can generate other voltages
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top