Desheng brand radio circuit based on CXA1191 integrated circuit

Industrial Router Crystal 3.2*2.5mm 3225 26M (26.000MHZ) 12PF 10PPM 20PPM 30PPM

Single chip microcomputer STM32L151CCU6

One-piece inductor

The CXA1191 is an AM/FM radio integrated circuit developed by SONY Corporation (here only the FM receiving part is used). The integrated circuit has high sensitivity, with tuning indication, electronic volume control and power amplifier circuit, and the CXA1691 can be directly interchanged.
The CXA1019 is Sony's early FM/Amplitude-specific radio integrated block. The CXA1191 is also Sony's FM/AM-specific radio integrated block, which performs better than the CXA1019. It can be seen from the internal block diagram that their internal structure is exactly the same, but they cannot be directly replaced in actual replacement. If you use CXA1191 to directly replace CXA1019, the output volume is very small. This is because the actual internal circuits of the power amplifiers of the two integrated blocks are not exactly the same, and the performance mainly lies in the 1 pin of the integrated block. The 1 pin of the CXA1019 is grounded in the circuit, while the 1 pin of the CXA1191 happens to be the output midpoint of the built-in amplifier. If the replacement is performed directly, the amplifier output signal will be mostly short-circuited (there is a built-in resistor), so the sound is small after direct replacement. If the 1 pin of the replaced CXA1191 is disconnected, it can be avoided that the signal is short-circuited. In the circuit drawing of the CXA1191, it was found that there is a 10nF capacitor connected to the 1st pin. As a result of the analysis, its 1 pin is specially designed to improve the sound quality. As long as you pay attention to this when substituting between them, the two integrated blocks can be completely replaced with each other.