One of the best reasons to buy dividend stocks on sale is that a cheaper price means  better-than-normal yields. A stock's price is inversely related to its dividend yield, and that means not only are you getting the stock at a cheap price when you buy it on the dip, but you also can secure a better payout along the way. Buying cheap dividend stocks is a great way to position your portfolio for some great returns as you can benefit from possible capital gains while also collecting recurring income.

Three dividend stocks that have fallen in the past month and that you can buy on the dip today are Bristol Myers Squibb (BMY -0.56%)Campbell Soup (CPB 2.09%), and Citigroup (C 1.23%). Because all of the stocks are in different industries, buying all three will also allow you to diversify your portfolio. Here's why they look like good buys right now.

1. Bristol Myers Squibb

Biopharmaceutical company Bristol Myers Squibb is down 6% in the past month, falling further than the S&P 500, which has declined less than 1% over the same period. There hasn't been any terribly bad news in recent weeks to explain the stock's fall, and it's likely due to the recent general weakness in the markets.

Bristol Myers Squibb did report its second-quarter results on Aug. 6, but the results were nothing to get too excited or pessimistic about. Although its sales of $10.1 billion looked impressive for the period ending June 30, the growth was mainly a result of its acquisition of Celgene, which the company completed in November. Celgene's Revlimid drug, which treats multiple myeloma, was the top-selling drug for Bristol Myers Squibb in the quarter with sales of $2.9 billion. The company incurred a net loss of $85 million during the period, mainly due to acquisition and integration-related expenses.

Bills and coins.

Image source: Getty Images.

Over the long term, the cancer-fighting company is stronger with Celgene's drugs, as they give Bristol Myers Squibb more room for growth. And that's great news for its dividend, because it means there could be more increases to the payout in the future. Today, the New York-based company pays its shareholders a quarterly dividend of $0.45, which yields 3%, above the typical S&P 500 yield of 2%. Over the past five years, Bristol Myers has raised its payouts by 22%, averaging a compounded annual growth rate of 4%.

At a forward price-to-earnings multiple of just 8, the stock is a cheap buy.  A year ago, it was trading at more than 11 times its future earnings.

2. Campbell Soup 

Shares of Campbell Soup are down 12% in the past month, with investors turning bearish on the stock after the New Jersey-based company released its fourth-quarter and year-end results on Sept. 3.

For the three-month period ending Aug. 2, Campbell reported net sales of $2.1 billion, up 18.4% year over year. Net earnings of $86 million were also a big improvement from the company's prior-period loss of $8 million. However, it may have been the packaged food company's guidance for the first quarter of fiscal 2021 that turned investors off. Management expects net sales for Q1 to grow by 5% to 7% -- perhaps lower than what investors were hoping for, especially with the COVID-19 pandemic still likely to keep many people home for the foreseeable future. The company's canned goods, soups, and other snacks have been popular pantry staples during the COVID-19 pandemic.

At a forward P/E of less than 16, the stock's also not an expensive buy (value investors normally look for a P/E of 15 or less). And with the decline in price, Campbell's $0.35 quarterly dividend now yields a little over 3%. The company last raised its dividend payments in 2017.

3. Citigroup

Another good dividend stock to round out your portfolio is top investment bank and financial services company Citigroup. The outlook for financial stocks isn't great right now, as the economy is in the midst of a recession and low interest rates are minimizing banks' earning potential. But over the long term, you'll be hard-pressed to find better, more stable investments than bank stocks.

In its second-quarter results, released July 14 for the period ending June 30, Citigroup reported revenue of $19.8 billion, up 5% year over year. However, its net income of $1.3 billion was down 73%, mainly a result of an increase in the bank's allowance for credit loss reserves.

There's been nothing recent to justify the bank stock's 14% decline in the past month. But the good news for investors is it creates an opportunity to buy a top bank stock at a reduced price. At a forward P/E of about 8.5, this is another good value stock investors can pick up today. At the end of 2019, the stock was trading at about 9.5 times its future earnings.

Citigroup currently pays investors a quarterly dividend of $0.51, yielding 4.5% annually. It's the highest yield on this list, and the company raised its payout by more than 13% just last year.

Which stock is the best buy today?

Before deciding which stock is the best of the three listed here, let's take a quick look at how all three are doing so far this year:

^SPX Chart

^SPX data by YCharts

While all the stocks are underperforming the S&P 500, Citigroup's been far and away the worst stock thus far. Let's also take a look at their forward P/E ratios together:

BMY PE Ratio (Forward) Chart

BMY PE Ratio (Forward) data by YCharts

Despite performing the best, Bristol Myers Squibb still appears to provide the most value to investors based on analysts' future earnings expectations. If you're looking for a balance of dividends and stability, then the healthcare stock looks to be the best buy right now.

However, if it's an income-generating stock you're after, then it's also hard not to want to buy shares of Citigroup. If the economy's able to recover sooner rather than later, buying the financial stock at its current price could look like a bargain a year or two from now.