ECE145a / 218a Bilateral Tuned Amplifier Design

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1 class notes, M. odwell, copyrighted 9 ECE145a / 8a Bilateral Tuned Amplifier Design Mark odwell University of California, anta Barbara rodwell@ece.ucsb.edu , fax

2 tability class notes, M. odwell, copyrighted 9 Unconditio nally stable if in 1 for all Equivalent ly : unconditionally stable if possible out L. 1 for all possible. A - port is 1) and a) b) 1- K An alternative B unconditionally stable if - 11 nd the condition is that thestability measure B ollet stability factor K 1, where 1 be positive, where

3 Potentially Unstable Amplifier class notes, M. odwell, copyrighted 9 ource stability circle Load stability circle - plane L - plane 11 1 out 1 1 in 1 This is a test at one specific frequency; must test at all frequencie s.

4 Unconditionally stable Amplifier class notes, M. odwell, copyrighted 9 ource stability circle Load stability circle - plane L - plane out in 1 This is a test at one specific frequency; must test at all frequencie s.

5 Why Might MA Not Exist? class notes, M. odwell, copyrighted 9 If the network is then by placing weforce out 1. potentially unstable, L within theload stability circle, The device then has negative input resistance. Appropriate choice will If of then cause oscillation. we adjust and the highest possiblegain, source impedance to obtain we will instead obtain infinite gain L (oscillation). Load stability circle 11 L L - plane The maximum available gain is infinite. This is *not *good.

6 Computing Maximum Available ain class notes, M. odwell, copyrighted 9 max P P AVA in wenow need iff PAVA Pload and Pin PAV L * out and s P P * in load AV T we must simultaneously solve in 11 L 1 L * and out 1 11 * L and then substituteinto T 1 1 in s s 1 1 L L The calculatio ns are long, and will not be shown.

7 Maximum Available ain class notes, M. odwell, copyrighted 9 max K K 1 where K (ollet stability factor). Notethat i.e. max K 1and B is only defined 1. for an unconditionally stable network,

8 class notes, M. odwell, copyrighted 9 tabilization: if device is potentially unstable - plane Adding series resistance stab as shownconstains Z gen tolie within stable region.

9 class notes, M. odwell, copyrighted 9 tabilization: if device is potentially unstable - plane If we include stab thestability cirle in the - port being simulated in the CAD software, moves outwardsas shown..

10 4 Obvious tabilization Methods class notes, M. odwell, copyrighted 9 - plane L - plane iven thesestability circles, four stabilization methodsare immediately apparent.

11 eries tabilization On Input class notes, M. odwell, copyrighted 9 - plane

12 hunt tabilization On Input class notes, M. odwell, copyrighted 9 - plane

13 eries tabilization On Output class notes, M. odwell, copyrighted 9 L - plane

14 hunt tabilization On Output class notes, M. odwell, copyrighted 9 L - plane

15 What ain Do We et After tabilization? class notes, M. odwell, copyrighted 9 Before stabilization After stabilizat ion * original *- parameters : ij *changed *- parameters : ij max K K 1 undefined (unstable) max stable max stable but K K K 1(just stable) 1 How do and compare to and?

16 Consider First The tabilization Network class notes, M. odwell, copyrighted 9 *stabilizer *- parameters : ij 11 ij *stabilizer *- parameters : ij 11 ij 11 ( ( stab stab Z Z ) ) Z Z 11 ( ( stab stab Y Y ) Y ) Y stab Z Z stab Y Y Key point is reciprocity : and

17 What ain Do We et After tabilization? class notes, M. odwell, copyrighted 9 T ij : transistor - parameters ij ij ij : stabilizer - parameters : stabilized transistor - parameters by inspection(mason's gain rules) : ij T ij b a 1 1 T T 1 b a 1 1 T T 1 T T T T!!!

18 Consider More Carefully class notes, M. odwell, copyrighted 9 Any cascaded T T blocks follow this relationship : ij Passive reciprocal 1 networksfollow this relationship : ij T ij We therefore find : T T tabilizin g does not change theratio of to.

19 What ain Do We et After tabilization? class notes, M. odwell, copyrighted 9 Before stabilization After stabilizat ion * original *- parameters : ij *changed *- parameters : ij max K K 1 undefined (unstable) max max_ stable K K 1 but K 1(just stable) and / / Maximum stable gain max_ stable

20 class notes, M. odwell, copyrighted 9 What Does Maximum table ain Mean??? The term :"Maximum stable gain" is tooshort tobe precise. M aximum stable gain is the maximum gain we can *if * we also guarantee that changing Z and Z L will not make the amplfier oscillate. obtain

21 Design Tools: Power ain Definitions class notes, M. odwell, copyrighted 9 Transducer ain Available ain Insertion ain Z s ij Z s ij Z s =Z o ij Z L =Z o Vgen Z L Vgen Z L =Z out * Vgen T P load / Pav, gen load power power available from generator general - case gain A P gain av, a / Pav, gen power available from amplifier power available from generator with output matched P av, a / Pav, gen power delivered to Zo load power available from Z generator gain in a 5 Ohm enviroment o P Operating ain P Z s =Z in * Vgen gain ij load / Pgen, delivered with input matched Z L load power power delivered from generator Maximum Available ain After impedance-matching: ij,matched Z s =Z Z o s =Z in * ij Z L =Z o match ij,raw match Z L =Z out * Vgen Vgen Max Pav, a / Pgen, delivered power available from amplifier power delivered from generator gain with both portsmatched, matched 11, matched max,raw, matched...mamay not exist......but only if unconditionally stable...

22 M/MA, db Unilateral Power ain class notes, M. odwell, copyrighted 9 1) Cancel device feedback w ith external lossless feedback 4 11 ) Matchinput and output esulting power gain is Mason's Unilateral ain U Y Y Y M onolithicamplifiers are not easily made unilateral U mostly of For simple BJT model, U rolls off U useful for extrapolation to find In III - V FETs, U shows peak from U hard to use for For bulk CMO, C ds U should be OK for historical relevance f max at - db/decade - - extrapolation is sheilded by substrate f max C ds s extrapolation to IC design f max d interaction 3 U 5 15 Common emitter Common base 1 Common Collector Frequency, Hz

23 class notes, M. odwell, copyrighted 9 Design Tools: tability Factors, tability Circles in L out 1 L 1 11 L 11 K ollet stability factor 1 11 det Load tability Circle ource tability Circle and B stability measure Unconditionally stable (stable with all 1 11, L if : det 1 Values of in L which make 1 beyond lies negative in Values of out which make 1 beyond lies negative out Negative port impedance negative- oscillator Tuning for highest gain infinite gain (oscillation)

24 Design Tools: Maximum table ain class notes, M. odwell, copyrighted 9 M aximum stable gain M Y Y Z Z circles at 5 Hz 17 circle stabilization methods 17 ij ij 5 ij ij 75 M results 5-1 MA 5 Hz Adding series/shunt resistance excludes source or load from unstable regions stabilizes

First: stabilize at the design frequency ---device is potentially unstable at 1 Hz

25 class notes, M. odwell, copyrighted 9 Design Procedure: imple ain-matched Amplifier _tabcircle1 First: stabilize at the design frequency ---device is potentially unstable at 1 Hz design frequency source stability circle: 5 Ohm on input will overstabilize the device indep(_tabcircle1) (. to 51.) After stabilizing (slightly over-stabilizing)

& p circles define the source & load impedances which the transistor must see available gain operating gain.

26 class notes, M. odwell, copyrighted 9 Design Procedure: imple ain-matched Amplifier econd: Determine required interface impedances The a & p circles define the source & load impedances which the transistor must see available gain operating gain...it is necessary to OVETABILIZE the device to move the a & p circles towards the mith chart center,opt L,opt Third: Design Input & Output Tuning Networks...to provide these impedances......added to device, the amplifier is not yet complete...

out-of-band stabilization potentially unstable below 75 Hz source & load stability

27 class notes, M. odwell, copyrighted 9 Design Procedure: imple ain-matched Amplifier Forth: Add out-of-band stabilization potentially unstable below 75 Hz source & load stability circles & 1,,...,1 Hz with frequency-selective series stabilization...caused only slight mistuning & slight gain 1 Hz...and is unconditionally stable above 1 Hz

28 Design Procedure: Effect of Line Losses class notes, M. odwell, copyrighted 9 Finally: adjusting for line losses high line skin effect losses reduced gain but line losses also increase stability factor loss in gain are partly recovered by reducing stabilization resistance & re-tuning the design line losses --no analytical procedure; just component tweaking line losses have severe impact...in VLI wiring environment...particularly at 5 + Hz...particularly with high-power amplifiers

gain, db, db Tuned Amplifier Examples class notes, M.

45 5 III-V HBT small-signal amplifiers 8 6 4 - -4 14 15 16 17 18 19

gain-tuned amplifiers limited applications Transmitters need power

29 gain, db, db Tuned Amplifier Examples class notes, M. odwell, copyrighted 9 3-stage cascode in 18 nm CMO III-V HBT small-signal amplifiers Frequency, Hz Frequency (Hz) Note: simple gain-tuned amplifiers limited applications Transmitters need power amplifiers: need output loadline-match, not gain-match eceivers need low-noise amplifiers: need input noise-match, not gain-match

Lecture 34 Amplifier Stability.

Lecture 34 Amplifier Stability. Whites, EE 481 ecture 34 Page 1 of 12 ecture 34 Amplifier tability. You ve seen in EE 322 that a simple model for a feedback oscillator has an amplifier and a feedback network connected as: Oscillation