TS615IPWT View Datasheet(PDF) - STMicroelectronics

Part Name

Description

MFG CO.

TS615IPWT

DUAL WIDE BAND OPERATIONAL AMPLIFIER WITH HIGH OUTPUT CURRENT

STMicroelectronics 

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TS615

Unlike the level Vo° required for a passive imped-

ance, Vo° will be smaller than 2Vo in our case. Let

us write Vo°=kVo with k the matching factor vary-

ing between 1 and 2. Assuming that the current

through R3 is negligible, it comes the following re-

sistance divider:

By fixing an arbitrary value of R2, (eq6) gives:

R3 = -------R-----2--------

1

–

2----R-----s--

RL

Ro = R-----L-k---V-+----o-2--R--R---L--s---1--

Finally, the values of R2 and R3 allow us to extract

R1 from (eq1), and it comes:

After choosing the k factor, Rs will equal to

1/2RL(k-1).

A good impedance matching assumes:

R o = 12-- RL,(eq5)

From (eq4) and (eq5) it becomes:

RR-----23-- = 1 – 2--R--R---L--s- ,(eq6)

R1 = ------------------------2----R-----2--------------------------,( eq7)

21 – RR-----23-- GL – 1 – RR-----23--

with GL the required gain.

Figure 77 : Components Calculation for

Impedance Matching Implementation

GL (gain for the

loaded system)

R1

R2 (=R4)

R3 (=R5)

Rs

Load viewed by

each driver

GL is fixed for the application requirements

GL=Vo/Vi=0.5(1+2R2/R1+R2/R3)/(1-R2/R3)

2R2/[2(1-R2/R3)GL-1-R2/R3]

Abritrary fixed

R2/(1-Rs/0.5RL)

0.5RL(k-1)

kRL/2

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