Upload
lukas-cavigelli
View
70
Download
5
Embed Size (px)
DESCRIPTION
Summary Analog Integrated Circuits ITET Lukas Cavigelli.pdf
Citation preview
ANALOG INTEGRATED CIRCUITS
Summary of the Lectures by Prof. Dr. Q. Huang
Lukas Cavigelli, December 2011
BASIC EQUATIONS & SMALL SIGNAL CIRCUITS
Small Signal Model: Only model differential behavior, use derivatives for all currents and voltages many ground-connections & short circuits. Use small letters.
BIPOLAR
Collector current: (
) ⁄
⁄
Transconductance:
⁄
Amplification: ⁄ for this lecture Hybrid- (small signal) model: at a certain operation point
for low frequencies:
|
[ ]
|
[ ]
|
[ ]
: bias current, : thermal voltage, : Early voltage Frequency Response: for low frequencies, -10dB/dec after ⁄ , | ( )| , more on foils
MOSFET (HERE: N-TYPE)
Triode/lin./ohmic region: if and (NMOS)
then ⏞
[ ( )
]
Active/saturation region: if and (NMOS)
( )
( )⏟
condition for saturation with PMOS: !! Cut-off/subth./weak-inversion region:
if
Pinch-Off point: and
[ ] [ ]
[ ] [ ] [ ] (√| [ ] | √| [ ]|)
[ ]
( [ ])⏟
√ [ ]
[ ]
[ ]
,
,
TYPICAL VALUES
MOS-TECHNOLOGY
for AMS C35 FETs: ( ): for and
3.3V NFET 3.3V PFET Unit
⁄
( ) ( )
⁄
⁄
⁄ ,
Reasonable values: BJT: , MOS: ⁄ , ⁄ , ,
Capacitors: MOS Capacitor: 5-12 fF/, , cheap MIM Cap: 1-5 fF/, highly linear, ±20%, 1µm
Resistors: Silicided Poly-Si Resistor 5-20 Ω/ (cheap) , ±20% Unsilicided Poly-Si Resistor 50-400 Ω/, ±20% but more accurate relations can be used
ANALOG SUBCIRCUITS
CURRENT MIRRORS
Simple CM:
→ √
( ⁄ )
MOS:
( ⁄ )
( ⁄ ) (
)
⏟
BJT:
and
⁄ if
from ⁄
COMMON-EMITTER & COMMON-SOURCE AMPLIFIERS
C-E, C-S Amplifier with resistive load:
, ⁄ ⁄
√
C-E, C-S Amplifier with Active Load: ideal current source instead of resistor
Common-Emitter Amplifier with non-ideal current source:
( )
(
)
→
( √ ⁄ )
√
( )
⁄
⁄ ⁄
( ) ( )
EMITTER & SOURCE DEGENERATION
Emitter Degeneration: increases input & output resistance, but reduces input resistance:
|
( ) ( ), if
output resistance:
|
(
(
))
→
( )
( )
Source Degeneration: same setup with MOSFET instead of BJT. increases output resistance, but reduces .
CASCODE STRUCTURE
Basic Cascode: Cascode = cascade to cathode
For FET:
For BJT: ( ) ( )
Regulated Cascode:
REFERENCES
Simple Current Source:
Widlar Current Source: for very small currents (µA) using only moderate resistor sizes
for BJT:
( ⁄ )
for FET: (not widely used)
√
( ⁄ )
,
√
( ⁄ )
√ √
Wilson Current Source:
Simple Voltage Source:
The bulk off all PFETs are connected to .
TRICKS
STUFF FROM THE EXERC ISE
High Swing Cascode Current Mirror:
usually , blabla
BASIC AMPIFIERS
UNSORTED
PMOS: , small-signal model accordingly flipped
ADMINISTRATIVE
Testing:
start: icdesign ams-hk3.70 -tech c35b3 & user: aic04 pass: 7qf-D3Lr user: aic20 pass: afto1]Xb
IMAGE ARCHIVE
sophisticated small-signal bjt
MOSFET hybrid-pi
MOSFET physical model
supply independent biasing
Single-Ended Amplifier
Emitter-Coupled pair
Source-Coupled pair
Differential Input to Single-Ended Output
SINGLE-STAGE OTA
AC ANALYSIS
mit ( ) , :
⏞
( ) [ (
)]
( ) [
( )⏟
]
Basic Idea: Stability problem in feedback conf., if gain>1 where 180°, because
DESIGN CONSTRAINTS
DC Gain:
| ( ) √
( ⁄ )
Output Swing:
√
( ⁄ )
, √
( ⁄ )
Slew Rate:
∫
GBP: (gain-BW-prod)
| |
UGBW: (unity-gain-BW)
|| | ( )
( )
Phase Margin: (
| |)
( )
SINGLE-STAGE CASCODE OTA
Comparison to non-cascode OTA: higher gain, higher output resistance, smaller output swing Additional pole of M9/M10-cascode at much higher frequency Gain Function:
( ) (
) (
)
with
DESIGN CONSTRAINTS
( ) ( )
( | |) ( | |)
mit
( ) und
:
o
( ), if | | | |
o (
| |)
⏟
(
| |)
⏟
⁄ Noise consideration: , because noise-power
, PMOS less noisy Typical performance of single-stage cascade OTA in 0.5µm CMOS process:
FOLDED CASCODE CMOS OTA
⁄ ⁄
( ) (
)
( ( ) )
Folded Cascode BiCMOS OTA: Difference: Replace M3,M4,M5,M6 with npn Q3,Q4,Q5,Q6 Comparison: improves by 6 dB, higher for npn BJTs, can be higher fastre OpAmp TODO: 2
nd Order Amplifier Model
REGULATED CASCODE
Principle:
NORTON-EQUIVALENT
( ) |
( ( ) ( )⁄ )
( ) ( ) | ( )
( )
SMALL-SIGNAL ANALYSIS
Applying KCL and simplifying with and and | | | | | |:
( ) (
)
FULLY DIFFERENTIAL O TA
SIMPLE FULLY DIFFERE NTIAL OTA
COMMON-MODE (CM) FEEDBACK
FULLY DIFFERENTIAL T ELESCOPIC CASCODE OTA
SWITCHED CM FEEDBACK
Example:
FULLY DIFFERENTIAL V S. SINGLE ENDED
Adv. of fully differential Amps Adv. of single ended Amps
Better PSRR (power supply rejection) Better CMRR (common mode reject.)
= diff. gain / common mode gain Double output swing for low volt. Higher SNR No extra diff. to single ended conv.
Less area consumption No extra common-mode feedback Requires less effort to design
TWO STAGE AMPLIFIERS
COMPARATORS