  The study of public opinion can provide us with valuable information. The
analysis of sentiment on social networks, such as Twitter or Facebook, has
become a powerful means of learning about the users' opinions and has a wide
range of applications. However, the efficiency and accuracy of sentiment
analysis is being hindered by the challenges encountered in natural language
processing (NLP). In recent years, it has been demonstrated that deep learning
models are a promising solution to the challenges of NLP. This paper reviews
the latest studies that have employed deep learning to solve sentiment analysis
problems, such as sentiment polarity. Models using term frequency-inverse
document frequency (TF-IDF) and word embedding have been applied to a series of
datasets. Finally, a comparative study has been conducted on the experimental
results obtained for the different models and input features
