Application information

TSX9291, TSX9292

18/31

DocID024568 Rev 4

4.4

Stability for gain = -1

TSX9291 and TSX9292 can be used in gain = -1 configuration (see Figure 36). However

some precautions must be taken regarding the setting of the Rg and Rf resistors. Effectively,

the input capacitance of the TSX929x series creates a pole with Rf and Rg. In high

frequency, this pole decreases the phase margin and also causes gain peaking. This effect

has a direct impact on the stability.

Figure 37 shows the peaking, depending on the values of the gain and feedback

resistances.

Figure 36. Configuration for gain = -1

Figure 37. Close loop gain vs. frequency

 

Cf

Rf

Rg

Vin

Vout

+

‐

+Vcc

-Vcc

1k

10k

100k

1M

10M

-30

-20

-10

0

10

20

Vcc=16V

Vicm=Vcc/2

Gain=-1

Cl=20pF

Frequency (Hz)