TS615IPWT(2004) View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

TS615IPWT
(Rev.:2004)

Dual Wide-Band Operational Amplifier with High Output Current

STMicroelectronics 

TS615

Increasing the Line Level Using Active Impedance Matching

Let us write Vo°=kVo, where k is the matching factor varying between 1 and 2. If we assume that the

current through R3 is negligible, we can calculate the output resistance, Ro:

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

After choosing the k factor, Rs will equal to 1/2RL(k-1).

For a good impedance matching we assume that:

Ro = 12-- RL

From Equation 9 and Equation 10, we derive:

Equation 10

RR-----23-- = 1 – 2--R--R---L--s--

By fixing an arbitrary value of R2, Equation 11 becomes:

R3 = 1-----–--R---2----2R----R-----L----s----

Finally, the values of R2 and R3 allow us to extract R1 from Equation 6, so that:

Equation 11

with GL the required gain.

R1 = ------------------------2----R-----2--------------------------

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

Table 7. 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]

Arbitrarily fixed

R2/(1-Rs/0.5RL)

0.5RL(k-1)

kRL/2

Equation 12

34/36

Share Link: